As opal things seem to pop up here on a regular basis, I thought a thread where it can be easily accessed would be better than it being lost in chat.

To kick it off I would like to mention the different opinions as to how opal occurs in one area, but not another. A study was conducted in NSW by the Mines Department around 30 years ago, and only related to opal in that State, another study was done in SA which borrowed heavily from the NSW study and again was only applicable to SA, however opal is found in different forms in Queensland and even WA.

These two studies, have been recycled in most publications ever since, which basically considers opal is formed by water seeping down to slowly dissolve the silica that later collects in underground cavities. This sounds good, but from talking to experienced miners on most Australian opal fields, very few believe this to be the case, as it does not match the facts underground.

The caves on the Nullarbor are officially also thought by most geologists to have been formed by water seeping down to dissolve the limestone to form the caves. This might be the case when you have a watercourse passing through the limestone to exist elsewhere, but when there is no outlet (as is the case on the Nullarbor) this explanation is not very satisfactory.

There have been a number of studies involving the formation of deep cavities within the limestone and out of eight geological opinions, 7 agreed with the water seeping down theory, whilst only one thought they had initially been formed by water being pushed up by hydrothermal activity. I am in agreement with the last opinion and if looked at from that point of view, it places a very different light on the situation.

This type of hydrothermal activity created by geological movement in deep aquifers that forces hot water to the surface; it is also applicable to opal formation and permits the underground environment to match up with this viewpoint, which it does not with the water down theory.

Anyone like to add?

smoke and mirrors.. http://www.internetopals.com/mining-movies/blower-working/blower-working.htm

Are you suggesting that limestone is dissolved by upwelling hot water?

roughbarked said:

smoke and mirrors.. http://www.internetopals.com/mining-movies/blower-working/blower-working.htm

Looks like Coober Pedy. The miners there with this type of equipment found it very costly to run, requiring a drum or two of diesel a week, which adds up if not on the opal. But without this type of equipment the chances of finding opal is greatly reduced; a real catch 22 situation. It’s what drove many out of the business.

I’ve never looked for opals since the price of diesel went past $1.40

PermeateFree said:

roughbarked said:

smoke and mirrors.. http://www.internetopals.com/mining-movies/blower-working/blower-working.htm

Looks like Coober Pedy. The miners there with this type of equipment found it very costly to run, requiring a drum or two of diesel a week, which adds up if not on the opal. But without this type of equipment the chances of finding opal is greatly reduced; a real catch 22 situation. It’s what drove many out of the business.

Correct. It is expensive. However many blowers are used in dugout creation and thus tend to pay for themselves when no opal is being found. At Coober Pedy and Lightning Ridge the finds are usually quite rich and if one has $14 million under the bed then running a blower is simply a labour saving device. Shifting mullock with a shovel quickly becomes a multiple handling nightmare.

morrie said:

Are you suggesting that limestone is dissolved by upwelling hot water?

Why, are you suggesting it is dissolved by seeping water?

Hot water gushing to the surface that could run for decades will certainly push out a lot of material and also wash it away. bit difficult to imagine how seepage could do the same but still form a cavity.

PermeateFree said:

morrie said:

Are you suggesting that limestone is dissolved by upwelling hot water?

Why, are you suggesting it is dissolved by seeping water?

Hot water gushing to the surface that could run for decades will certainly push out a lot of material and also wash it away. bit difficult to imagine how seepage could do the same but still form a cavity.

You didn’t answer the question.

roughbarked said:

PermeateFree said:

roughbarked said:

smoke and mirrors.. http://www.internetopals.com/mining-movies/blower-working/blower-working.htm

Looks like Coober Pedy. The miners there with this type of equipment found it very costly to run, requiring a drum or two of diesel a week, which adds up if not on the opal. But without this type of equipment the chances of finding opal is greatly reduced; a real catch 22 situation. It’s what drove many out of the business.

Correct. It is expensive. However many blowers are used in dugout creation and thus tend to pay for themselves when no opal is being found. At Coober Pedy and Lightning Ridge the finds are usually quite rich and if one has $14 million under the bed then running a blower is simply a labour saving device. Shifting mullock with a shovel quickly becomes a multiple handling nightmare.

If only! These blowers are very common in the opal fields and not all can be used to help construct underground homes, especially when most people are either leaving the industry or moving elsewhere.

morrie said:

PermeateFree said:

morrie said:

Are you suggesting that limestone is dissolved by upwelling hot water?

Why, are you suggesting it is dissolved by seeping water?

Hot water gushing to the surface that could run for decades will certainly push out a lot of material and also wash it away. bit difficult to imagine how seepage could do the same but still form a cavity.

You didn’t answer the question.

Didn’t I? Please read again!

PermeateFree said:

morrie said:

PermeateFree said:

Why, are you suggesting it is dissolved by seeping water?

Hot water gushing to the surface that could run for decades will certainly push out a lot of material and also wash it away. bit difficult to imagine how seepage could do the same but still form a cavity.

You didn’t answer the question.

Didn’t I? Please read again!

Pushing out and washing away isn’t necessarily dissolving. But I will assume that you are saying that the limestone is dissolved by hot water and transported to the surface.
Yes or No would have sufficed and no I am not implying anything.

I note that there appears to be quite a few gaps in understanding of the nature of cavernous limestones, of the dissolution processes that occur, and of groundwater movement.

However, as I am but an unqualified Old Fart, I will leave you to your ponderings.

morrie said:

PermeateFree said:

morrie said:

You didn’t answer the question.

Didn’t I? Please read again!

Pushing out and washing away isn’t necessarily dissolving. But I will assume that you are saying that the limestone is dissolved by hot water and transported to the surface.
Yes or No would have sufficed and no I am not implying anything.

I think you ought to read my initial post again, because you are doing your usual distortion of facts and nit-picking. Wouldn’t mind except you are nearly always just trying to make trouble.

Geoff D said:

I note that there appears to be quite a few gaps in understanding of the nature of cavernous limestones, of the dissolution processes that occur, and of groundwater movement.

However, as I am but an unqualified Old Fart, I will leave you to your ponderings.

This thread is supposed to be about opal, not limestone. That was only introduced to point out a different professional opinion concerning the seeping down of water compared to the hydrothermal effect of water going the other way. For your information I have encountered at the foot of the limestone cliffs a large (too heavy to move) solid lump of silica that had obviously been formed by hydrothermal activity. But there again and according to morrie I am an old fart too. But not to worry, as there seems to be a lot of old farts in this forum.

PermeateFree said:

I think you ought to read my initial post again, because you are doing your usual distortion of facts and nit-picking. Wouldn’t mind except you are nearly always just trying to make trouble.

“There have been a number of studies involving the formation of deep cavities within the limestone and out of eight geological opinions, 7 agreed with the water seeping down theory”

87.5% of experts in the field think that the caves are formed by seeping down. I’d say the science is settled.

I’d like to know why Australia (almost) has the monopoly on opal mining. Why are there so many opals here?

morrie said:

PermeateFree said:

I think you ought to read my initial post again, because you are doing your usual distortion of facts and nit-picking. Wouldn’t mind except you are nearly always just trying to make trouble.

“There have been a number of studies involving the formation of deep cavities within the limestone and out of eight geological opinions, 7 agreed with the water seeping down theory”

87.5% of experts in the field think that the caves are formed by seeping down. I’d say the science is settled.

So you think science is all done and dusted? So much for your scientific integrity. :))))

PermeateFree said:

morrie said:

PermeateFree said:

I think you ought to read my initial post again, because you are doing your usual distortion of facts and nit-picking. Wouldn’t mind except you are nearly always just trying to make trouble.

“There have been a number of studies involving the formation of deep cavities within the limestone and out of eight geological opinions, 7 agreed with the water seeping down theory”

87.5% of experts in the field think that the caves are formed by seeping down. I’d say the science is settled.

So you think science is all done and dusted? So much for your scientific integrity. :))))

PermeateFree said:

morrie said:

PermeateFree said:

I think you ought to read my initial post again, because you are doing your usual distortion of facts and nit-picking. Wouldn’t mind except you are nearly always just trying to make trouble.

“There have been a number of studies involving the formation of deep cavities within the limestone and out of eight geological opinions, 7 agreed with the water seeping down theory”

87.5% of experts in the field think that the caves are formed by seeping down. I’d say the science is settled.

So you think science is all done and dusted? So much for your scientific integrity. :))))

Well thats the ironing done and dusted at least.

I know nothing of seepage in limestone but I am enjoying the dancing.

Divine Angel said:

I’d like to know why Australia (almost) has the monopoly on opal mining. Why are there so many opals here?

It is to do with the size of Australia’s inland sea during the Craterous that deposited the fine clays in which opal needs to form. Secondly over these deposits is the Artesian Basin, a massive body of underground water. When these waters are forced to the surface (usually around its outer edge) and other conditions are right then opal might form.

If on the other hand that opal formed via the seepage of water from the surface, then it should have formed all over the place, but it doesn’t.

Divine Angel said:

I’d like to know why Australia (almost) has the monopoly on opal mining. Why are there so many opals here?

.
Stable continental interior.
Flat-lying, weakly porous, weakly fractured sedimentary rock.
Rock matrix dominated by smectite clays (swell with water).
Evaporation exceeded precipitation in many years.

Michael V said:

Divine Angel said:

I’d like to know why Australia (almost) has the monopoly on opal mining. Why are there so many opals here?

.
Stable continental interior.
Flat-lying, weakly porous, weakly fractured sedimentary rock.
Rock matrix dominated by smectite clays (swell with water).
Evaporation exceeded precipitation in many years.

In opal producing areas there is a layer of calcrete or silcrete that creates an impermeable barrier for surface water. Where this solid layer does not exist there is no opal. Also opal is found only towards the outer areas of the Artisan Basin, so why would this be so?

PermeateFree said:

Divine Angel said:

I’d like to know why Australia (almost) has the monopoly on opal mining. Why are there so many opals here?

It is to do with the size of Australia’s inland sea during the Craterous that deposited the fine clays in which opal needs to form. Secondly over these deposits is the Artesian Basin, a massive body of underground water. When these waters are forced to the surface (usually around its outer edge) and other conditions are right then opal might form.

If on the other hand that opal formed via the seepage of water from the surface, then it should have formed all over the place, but it doesn’t.

.

Well, that doesn’t really explain the Lightning Ridge group of opal fields, which are not near the edge of the Great Australian Basin. It also doesn’t explain why opal is not found under Holocene alluvium. The GAB artesion water would surely leak out where the reduced level of the Cretaceous sediments is lower. Why are opals not found at mound springs, where the water actually leaks out of the GAB?

PermeateFree said:

Divine Angel said:

I’d like to know why Australia (almost) has the monopoly on opal mining. Why are there so many opals here?

It is to do with the size of Australia’s inland sea during the Craterous that deposited the fine clays in which opal needs to form. Secondly over these deposits is the Artesian Basin, a massive body of underground water. When these waters are forced to the surface (usually around its outer edge) and other conditions are right then opal might form.

If on the other hand that opal formed via the seepage of water from the surface, then it should have formed all over the place, but it doesn’t.

How long ago was this Craterous period?

morrie said:

How long ago was this Craterous period?

Around about the Cretaceous, I guess.

http://en.wikipedia.org/wiki/Late_Heavy_Bombardment

the craterous period.

;-)

Boris said:

http://en.wikipedia.org/wiki/Late_Heavy_Bombardment

the craterous period.

;-)

golf clap

Thankyou MV.

Michael V said:

PermeateFree said:

Divine Angel said:

I’d like to know why Australia (almost) has the monopoly on opal mining. Why are there so many opals here?

It is to do with the size of Australia’s inland sea during the Craterous that deposited the fine clays in which opal needs to form. Secondly over these deposits is the Artesian Basin, a massive body of underground water. When these waters are forced to the surface (usually around its outer edge) and other conditions are right then opal might form.

If on the other hand that opal formed via the seepage of water from the surface, then it should have formed all over the place, but it doesn’t.

.

Well, that doesn’t really explain the Lightning Ridge group of opal fields, which are not near the edge of the Great Australian Basin. It also doesn’t explain why opal is not found under Holocene alluvium. The GAB artesion water would surely leak out where the reduced level of the Cretaceous sediments is lower. Why are opals not found at mound springs, where the water actually leaks out of the GAB?

Lightning Ridge IS on the outer edge of the Artesian Basin. The reason the mound springs do not form opal is the lack of a silcrete or similar capping so pressure can build and create an oven type environment. They also need an arrangement of major and minor slides to contain this heat. There are other factors that I will not add at this stage.

It was Boris’s comment, but I’ll take the accolades, thanks.

i think DA was thanking you for the answer to her question. not my humour. so nick orf…

morrie said:

Are you suggesting that limestone is dissolved by upwelling hot water?

Are you alluding to this Morrie?

Sorry for the Fahrenheit.

morrie said:

PermeateFree said:

Divine Angel said:

I’d like to know why Australia (almost) has the monopoly on opal mining. Why are there so many opals here?

It is to do with the size of Australia’s inland sea during the Craterous that deposited the fine clays in which opal needs to form. Secondly over these deposits is the Artesian Basin, a massive body of underground water. When these waters are forced to the surface (usually around its outer edge) and other conditions are right then opal might form.

If on the other hand that opal formed via the seepage of water from the surface, then it should have formed all over the place, but it doesn’t.

How long ago was this Craterous period?

Morrie I get a little pissed off with you. Do you know why I make spelling errors? It is because I have suffered my entire life with Dyslexia. Had it not been for computers and spell checkers my life would still be greatly disadvantaged, but I have worked bloody hard to largely overcome my disability and I don’t need some smartarse arrogant prick like you to be continually throwing it in my face. So why don’t sod off you irritating little worm!

PermeateFree said:

Michael V said:

PermeateFree said:

It is to do with the size of Australia’s inland sea during the Craterous that deposited the fine clays in which opal needs to form. Secondly over these deposits is the Artesian Basin, a massive body of underground water. When these waters are forced to the surface (usually around its outer edge) and other conditions are right then opal might form.

If on the other hand that opal formed via the seepage of water from the surface, then it should have formed all over the place, but it doesn’t.

.

Well, that doesn’t really explain the Lightning Ridge group of opal fields, which are not near the edge of the Great Australian Basin. It also doesn’t explain why opal is not found under Holocene alluvium. The GAB artesion water would surely leak out where the reduced level of the Cretaceous sediments is lower. Why are opals not found at mound springs, where the water actually leaks out of the GAB?

Lightning Ridge IS on the outer edge of the Artesian Basin. The reason the mound springs do not form opal is the lack of a silcrete or similar capping so pressure can build and create an oven type environment. They also need an arrangement of major and minor slides to contain this heat. There are other factors that I will not add at this stage.

.

If Lightning ridge is at the outer edge of the GAB, then why is the artesian water about 1000 metres deep there?

Look at the geologic maps carefully.

Silcrete is rarely a continuous cap.

“Slides” – firstly use a geological term to continue a geological discussion. Second, how can these structures “contain” this heat?

A good place to start on the literature is to read the works of Brian Senior. Other people have also published well researched scientific works. Brian is still an active researcher.

Boris said:

i think DA was thanking you for the answer to her question. not my humour. so nick orf…

.

Oh, I see. Castigation complete?

PM 2Ring said:

morrie said:

Are you suggesting that limestone is dissolved by upwelling hot water?

Are you alluding to this Morrie?

Sorry for the Fahrenheit.

That was in my mind, PM, yes. There are places where hot water springs bring dissolved calcium to the surface though.

morrie said:

That was in my mind, PM, yes. There are places where hot water springs bring dissolved calcium to the surface though.

And I guess it’d generally hold onto its calcium when it cools, due to the counter-intuitive solubility curve, assuming the pH near the surface doesn’t intervene.

PM 2Ring said:

morrie said:

That was in my mind, PM, yes. There are places where hot water springs bring dissolved calcium to the surface though.

And I guess it’d generally hold onto its calcium when it cools, due to the counter-intuitive solubility curve, assuming the pH near the surface doesn’t intervene.

.

pH is the single most important factor in the dissolution of CaCo3.

PM 2Ring said:

morrie said:

That was in my mind, PM, yes. There are places where hot water springs bring dissolved calcium to the surface though.

And I guess it’d generally hold onto its calcium when it cools, due to the counter-intuitive solubility curve, assuming the pH near the surface doesn’t intervene.

No, because it requires carbon dioxide to keep it in solution and once the pressure is reduced the carbon dioxide goes to the atmosphere and the the calcium carbonate is deposited. That is how travertine marble is formed.

morrie said:

PM 2Ring said:

And I guess it’d generally hold onto its calcium when it cools, due to the counter-intuitive solubility curve, assuming the pH near the surface doesn’t intervene.

No, because it requires carbon dioxide to keep it in solution and once the pressure is reduced the carbon dioxide goes to the atmosphere and then the calcium carbonate is deposited. That is how travertine marble is formed.

Ah. That makes sense.

Michael V said:

PermeateFree said:

Michael V said:

.

Well, that doesn’t really explain the Lightning Ridge group of opal fields, which are not near the edge of the Great Australian Basin. It also doesn’t explain why opal is not found under Holocene alluvium. The GAB artesion water would surely leak out where the reduced level of the Cretaceous sediments is lower. Why are opals not found at mound springs, where the water actually leaks out of the GAB?

Lightning Ridge IS on the outer edge of the Artesian Basin. The reason the mound springs do not form opal is the lack of a silcrete or similar capping so pressure can build and create an oven type environment. They also need an arrangement of major and minor slides to contain this heat. There are other factors that I will not add at this stage.

.

If Lightning ridge is at the outer edge of the GAB, then why is the artesian water about 1000 metres deep there?

Look at the geologic maps carefully.

Silcrete is rarely a continuous cap.

“Slides” – firstly use a geological term to continue a geological discussion. Second, how can these structures “contain” this heat?

A good place to start on the literature is to read the works of Brian Senior. Other people have also published well researched scientific works. Brian is still an active researcher.

Hello, I have studied the maps – have you? And what is your problem with the water being 1000 ft deep at that point?

No, silcrete occurs when the surface silica reforms to bond with the clay to form a very hard capping and you are quite right, it does not occur everywhere, but it does readily occur in the vicinity of hydroponic activity. Think you are arguing for me there.

Slides are not just massive slippages, but where they do occur it lifts the entire area, which in the process will create many smaller slides around it, these also will slip sideways to form numerous small contained areas where the horizontal bedding is displaced to stop or greatly restrict sideways movement along these bedding zones. This then permits an oven-like environment to form and that will cook the initial soft clays to form the sandstone (miners terminology) and the silica to melt and reform into hopefully opal if all these and other conditions are suitable.

>Do you know why I make spelling errors? It is because I have suffered my entire life with Dyslexia.

Well that does explain a few things. I won’t pick on your spelling mistakes any more.

morrie said:

>Do you know why I make spelling errors? It is because I have suffered my entire life with Dyslexia.

Well that does explain a few things. I won’t pick on your spelling mistakes any more.

Hope that doesn’t fuck up your nit-picking too much.

PermeateFree said:

morrie said:

>Do you know why I make spelling errors? It is because I have suffered my entire life with Dyslexia.

Well that does explain a few things. I won’t pick on your spelling mistakes any more.

Hope that doesn’t fuck up your nit-picking too much.

No worries. Plenty of scope.

Michael V said:

PermeateFree said:

Divine Angel said:

I’d like to know why Australia (almost) has the monopoly on opal mining. Why are there so many opals here?

It is to do with the size of Australia’s inland sea during the Craterous that deposited the fine clays in which opal needs to form. Secondly over these deposits is the Artesian Basin, a massive body of underground water. When these waters are forced to the surface (usually around its outer edge) and other conditions are right then opal might form.

If on the other hand that opal formed via the seepage of water from the surface, then it should have formed all over the place, but it doesn’t.

.

Well, that doesn’t really explain the Lightning Ridge group of opal fields, which are not near the edge of the Great Australian Basin. It also doesn’t explain why opal is not found under Holocene alluvium. The GAB artesion water would surely leak out where the reduced level of the Cretaceous sediments is lower. Why are opals not found at mound springs, where the water actually leaks out of the GAB?

>>The Great Artesian Basin

The Artesian Baths in Lightning Ridge are a natural resource – the mineral-rich water is naturally hot, forced up from a kilometer underground from the Great Artesian Basin – a massive artesian groundwater basin covering one-fifth of Australia, one of the largest in the world.<<

http://www.bigtrip.com.au/things-to-see/australia/nsw/lightning-ridge-artesian-baths.html

Just for the record.

PermeateFree said:

Michael V said:

PermeateFree said:

Lightning Ridge IS on the outer edge of the Artesian Basin. The reason the mound springs do not form opal is the lack of a silcrete or similar capping so pressure can build and create an oven type environment. They also need an arrangement of major and minor slides to contain this heat. There are other factors that I will not add at this stage.

.

If Lightning ridge is at the outer edge of the GAB, then why is the artesian water about 1000 metres deep there?

Look at the geologic maps carefully.

Silcrete is rarely a continuous cap.

“Slides” – firstly use a geological term to continue a geological discussion. Second, how can these structures “contain” this heat?

A good place to start on the literature is to read the works of Brian Senior. Other people have also published well researched scientific works. Brian is still an active researcher.

Hello, I have studied the maps – have you? And what is your problem with the water being 1000 ft deep at that point?

No, silcrete occurs when the surface silica reforms to bond with the clay to form a very hard capping and you are quite right, it does not occur everywhere, but it does readily occur in the vicinity of hydroponic activity. Think you are arguing for me there.

Slides are not just massive slippages, but where they do occur it lifts the entire area, which in the process will create many smaller slides around it, these also will slip sideways to form numerous small contained areas where the horizontal bedding is displaced to stop or greatly restrict sideways movement along these bedding zones. This then permits an oven-like environment to form and that will cook the initial soft clays to form the sandstone (miners terminology) and the silica to melt and reform into hopefully opal if all these and other conditions are suitable.

.

You do understand that artesian water is in and near the base of the artesian basin? In that case, the base of the basin is 1000 metres below the surface (give or take a bit). That means the edge of the basin is a long way away.

As I said, silcrete is rarely a continuous capping. It often occurs as isolated cobbles to boulders on or near the surface. That is certainly the case in the Lightning Ridge region, and over many other parts of Australia.

Slides: this is a non-defined term. Use a term with a definition, please.

Do you have any idea of the temperature that silica melts at? Very high. 1600+°C. The opal-bearing claystones (devitrified volcanic ash) would melt way below that temperature. We would see massive volcanism during the opal-forming phase in your model. We don’t.

morrie said:

PermeateFree said:

morrie said:

>Do you know why I make spelling errors? It is because I have suffered my entire life with Dyslexia.

Well that does explain a few things. I won’t pick on your spelling mistakes any more.

Hope that doesn’t fuck up your nit-picking too much.

No worries. Plenty of scope.

With someone like you I can believe that, only try not to get too carried away with your vindictiveness.

PermeateFree said:

morrie said:

PermeateFree said:

Hope that doesn’t fuck up your nit-picking too much.

No worries. Plenty of scope.

With someone like you I can believe that, only try not to get too carried away with your vindictiveness.

He tends to focus on your wrongness…

PermeateFree said:

Michael V said:

PermeateFree said:

It is to do with the size of Australia’s inland sea during the Craterous that deposited the fine clays in which opal needs to form. Secondly over these deposits is the Artesian Basin, a massive body of underground water. When these waters are forced to the surface (usually around its outer edge) and other conditions are right then opal might form.

If on the other hand that opal formed via the seepage of water from the surface, then it should have formed all over the place, but it doesn’t.

.

Well, that doesn’t really explain the Lightning Ridge group of opal fields, which are not near the edge of the Great Australian Basin. It also doesn’t explain why opal is not found under Holocene alluvium. The GAB artesion water would surely leak out where the reduced level of the Cretaceous sediments is lower. Why are opals not found at mound springs, where the water actually leaks out of the GAB?

>>The Great Artesian Basin

The Artesian Baths in Lightning Ridge are a natural resource – the mineral-rich water is naturally hot, forced up from a kilometer underground from the Great Artesian Basin – a massive artesian groundwater basin covering one-fifth of Australia, one of the largest in the world.<<

http://www.bigtrip.com.au/things-to-see/australia/nsw/lightning-ridge-artesian-baths.html

Just for the record.

.

I am well aware of the artesian baths at Lightning Ridge. The bored for that water in 1960 or 1961. There are many aquacludes between the water-bearing horizons and the surface.

+y

They…

I’ve been looking about for some simple illustrations of the solubility of silica versus pH and temperature, and have discovered that it is not a subject that can be simplified. But under ‘just right’ conditions, you can have quite high concentrations of dissolved silica in ground and volcanic waters.

Michael V said:

PermeateFree said:

This then permits an oven-like environment to form and that will cook the initial soft clays to form the sandstone (miners terminology) and the silica to melt and reform into hopefully opal if all these and other conditions are suitable.

[…]

Do you have any idea of the temperature that silica melts at? Very high. 1600+°C. The opal-bearing claystones (devitrified volcanic ash) would melt way below that temperature. We would see massive volcanism during the opal-forming phase in your model. We don’t.

I can understand a bit of heat being involved in opal formation, but surely not enough to actually melt silica! I was under the impression that opal is amorphous hydrated silica, essentially a form of silica gel, so too much heat would tend to bake the water out of it and thus disrupt its structure, although I guess it could cope with wet heat.

PM 2Ring said:

Michael V said:

PermeateFree said:

This then permits an oven-like environment to form and that will cook the initial soft clays to form the sandstone (miners terminology) and the silica to melt and reform into hopefully opal if all these and other conditions are suitable.

[…]

Do you have any idea of the temperature that silica melts at? Very high. 1600+°C. The opal-bearing claystones (devitrified volcanic ash) would melt way below that temperature. We would see massive volcanism during the opal-forming phase in your model. We don’t.

I can understand a bit of heat being involved in opal formation, but surely not enough to actually melt silica! I was under the impression that opal is amorphous hydrated silica, essentially a form of silica gel, so too much heat would tend to bake the water out of it and thus disrupt its structure, although I guess it could cope with wet heat.

I think the term melt is being used to describe dissolution in this instance.

Hello, I have studied the maps – have you? And what is your problem with the water being 1000 ft deep at that point?

No, silcrete occurs when the surface silica reforms to bond with the clay to form a very hard capping and you are quite right, it does not occur everywhere, but it does readily occur in the vicinity of hydroponic activity. Think you are arguing for me there.

Slides are not just massive slippages, but where they do occur it lifts the entire area, which in the process will create many smaller slides around it, these also will slip sideways to form numerous small contained areas where the horizontal bedding is displaced to stop or greatly restrict sideways movement along these bedding zones. This then permits an oven-like environment to form and that will cook the initial soft clays to form the sandstone (miners terminology) and the silica to melt and reform into hopefully opal if all these and other conditions are suitable.
.

>>You do understand that artesian water is in and near the base of the artesian basin? In that case, the base of the basin is 1000 metres below the surface (give or take a bit). That means the edge of the basin is a long way away.<<

Are you suggesting that the hot water baths in Lightning Ridge and hence likely to affect the opal producing area is NOT from the Artesian Basin? Or are you just nit-picking for the sake of it?

>>As I said, silcrete is rarely a continuous capping. It often occurs as isolated cobbles to boulders on or near the surface. That is certainly the case in the Lightning Ridge region, and over many other parts of Australia.<<

You are apparently arguing with yourself on this one.

>>Slides: this is a non-defined term. Use a term with a definition, please.<<

Oh you poor deprived geologist! I’m guessing another senseless nit-picking exercise.

>>Do you have any idea of the temperature that silica melts at? Very high. 1600+°C. The opal-bearing claystones (devitrified volcanic ash) would melt way below that temperature. We would see massive volcanism during the opal-forming phase in your model. We don’t.<<

As running cold water can cause silica to dissolve over time, then what I am referring (also over a long period of time) in a hot pressure-cooker is quite feasible. There is no need for volcanic activity, plus you are condoning a situation where cold water seeping down will actually create opal. Wish you would be a little more objective, rather than following in morrie’s footsteps.

Darragh and Gaskin first discovered the structure of opal in the early 60’s, and developed a low-temperature model that explained the formation of both common and precious opal. The model must be pretty reasonable, because precious opal was first synthesised in the ’70’s.

I note here that opal is not found in high-temperature regimes. Opal is always found infilling voids in low-temperature regimes.

Pfft. I refuse to believe opal even exists.

PM 2Ring said:

Michael V said:

PermeateFree said:

This then permits an oven-like environment to form and that will cook the initial soft clays to form the sandstone (miners terminology) and the silica to melt and reform into hopefully opal if all these and other conditions are suitable.

[…]

Do you have any idea of the temperature that silica melts at? Very high. 1600+°C. The opal-bearing claystones (devitrified volcanic ash) would melt way below that temperature. We would see massive volcanism during the opal-forming phase in your model. We don’t.

I can understand a bit of heat being involved in opal formation, but surely not enough to actually melt silica! I was under the impression that opal is amorphous hydrated silica, essentially a form of silica gel, so too much heat would tend to bake the water out of it and thus disrupt its structure, although I guess it could cope with wet heat.

.

Opal is hydrated silica. It has structure (micelles). Not much temperature is required to destroy opal.

PM 2Ring said:

Michael V said:

PermeateFree said:

This then permits an oven-like environment to form and that will cook the initial soft clays to form the sandstone (miners terminology) and the silica to melt and reform into hopefully opal if all these and other conditions are suitable.

[…]

Do you have any idea of the temperature that silica melts at? Very high. 1600+°C. The opal-bearing claystones (devitrified volcanic ash) would melt way below that temperature. We would see massive volcanism during the opal-forming phase in your model. We don’t.

I can understand a bit of heat being involved in opal formation, but surely not enough to actually melt silica! I was under the impression that opal is amorphous hydrated silica, essentially a form of silica gel, so too much heat would tend to bake the water out of it and thus disrupt its structure, although I guess it could cope with wet heat.

What I am saying is the sandstone was formed from a moist pliable clay, which if you dig under the opal sandstone region, usually within 60 feet from the surface, you will encounter the same soft clay. This clay level is well known by the miners who then know there is no lower opal level, or when drilling (prospecting) they know to stop once this clay is reached.

morrie said:

PM 2Ring said:

I can understand a bit of heat being involved in opal formation, but surely not enough to actually melt silica! I was under the impression that opal is amorphous hydrated silica, essentially a form of silica gel, so too much heat would tend to bake the water out of it and thus disrupt its structure, although I guess it could cope with wet heat.

I think the term melt is being used to describe dissolution in this instance.

Ah, ok. Fair enough, I s’pose, but a bit confusing.

carry on citizens, nothing to see here

PM 2Ring said:

I can understand a bit of heat being involved in opal formation, but surely not enough to actually melt silica! I was under the impression that opal is amorphous hydrated silica, essentially a form of silica gel, so too much heat would tend to bake the water out of it and thus disrupt its structure, although I guess it could cope with wet heat.

Opal formation is a result of hydrothermal processes. Essentially mineral bearing hydrothermal solutions cool and precipitate out the minerals that form, in this instance, the opal.

>>You do understand that artesian water is in and near the base of the artesian basin? In that case, the base of the basin is 1000 metres below the surface (give or take a bit). That means the edge of the basin is a long way away.<<

Are you suggesting that the hot water baths in Lightning Ridge and hence likely to affect the opal producing area is NOT from the Artesian Basin? Or are you just nit-picking for the sake of it?

———————————————————————————————————————————
No, I am not. I am saying the basin is 1000 m deep at that point. The margin of the basin is a long way away. It is not close by.
…………………………………………………………………………………………
>>As I said, silcrete is rarely a continuous capping. It often occurs as isolated cobbles to boulders on or near the surface. That is certainly the case in the Lightning Ridge region, and over many other parts of Australia.<<

You are apparently arguing with yourself on this one.
——————————————————————————————————-

You were the person asserting that a continuous capping of silcrete or similar was a necessary requirement of your model. I say that rarely occors, and also pointed out a well-known opal-bearing region where the silcrete is sporadic, usually isolated cobbles.

……………………………………………………………………………….

>>Slides: this is a non-defined term. Use a term with a definition, please.<<

Oh you poor deprived geologist! I’m guessing another senseless nit-picking exercise.
————————————————————————————————————-
Name-calling is rude and counterproductive. I object to that sort of behaviour

I have no problems with you using a well-defined term, or if there is none, to define one yourself. We are certainly going to find it dificcult to discuss this matter if we don’t have a common language. I mean, that’s how good communiction occurs – where all words are defined and their meanings are understood by all.

……………………………………………………………………………….

>>Do you have any idea of the temperature that silica melts at? Very high. 1600+°C. The opal-bearing claystones (devitrified volcanic ash) would melt way below that temperature. We would see massive volcanism during the opal-forming phase in your model. We don’t.<<

As running cold water can cause silica to dissolve over time, then what I am referring (also over a long period of time) in a hot pressure-cooker is quite feasible. There is no need for volcanic activity, plus you are condoning a situation where cold water seeping down will actually create opal. Wish you would be a little more objective, rather than following in morrie’s footsteps.
—————————————————————————
You prosed that the silica melted. I merely pointed out silica’s melting temperature, and that that temperature would likely melt the entire enclosing rock mass. The injuection of that amount of heat would be seen as massive volcanism. We simply don’t see that during the opal-forming phase.

Again, please resist name-calling and name-calling by association. These discussion techniques are rude, quite hurtful and very disrespectful.

PermeateFree said:

>>You do understand that artesian water is in and near the base of the artesian basin? In that case, the base of the basin is 1000 metres below the surface (give or take a bit). That means the edge of the basin is a long way away.<<

Are you suggesting that the hot water baths in Lightning Ridge and hence likely to affect the opal producing area is NOT from the Artesian Basin? Or are you just nit-picking for the sake of it?

I think MV is saying that Lightning Ridge is some distance from the nearest edge of the Great Artesian Basin.

Michael V said:

Darragh and Gaskin first discovered the structure of opal in the early 60’s, and developed a low-temperature model that explained the formation of both common and precious opal. The model must be pretty reasonable, because precious opal was first synthesised in the ’70’s.

I note here that opal is not found in high-temperature regimes. Opal is always found infilling voids in low-temperature regimes.

The arrangement of microscopic silica spheres and the gaps between them , coupled with light deflection creates the opal colours, or if the gaps are filled in then worthless potch is the result. There is no dispute about this from anyone, least of all me. What we are trying to discuss here is how this could naturally occur.

As for temperature zones over time. For a start the heat from the pressure cooking situation would never be described as being in a ‘high’ temperature zone. And secondly, when geological movement creates hydrothermal zones, once the aquifer stabilises then the water flow will stop and the heat will dissipate. And yes opal commonly fills voids, but exactly when in a variety of circumstances where opal is found is less certain.

diddly-squat said:

PM 2Ring said:

I can understand a bit of heat being involved in opal formation, but surely not enough to actually melt silica! I was under the impression that opal is amorphous hydrated silica, essentially a form of silica gel, so too much heat would tend to bake the water out of it and thus disrupt its structure, although I guess it could cope with wet heat.

Opal formation is a result of hydrothermal processes. Essentially mineral bearing hydrothermal solutions cool and precipitate out the minerals that form, in this instance, the opal.

Except Michael V just said:

“Darragh and Gaskin first discovered the structure of opal in the early 60’s, and developed a low-temperature model that explained the formation of both common and precious opal. The model must be pretty reasonable, because precious opal was first synthesised in the ’70’s.

I note here that opal is not found in high-temperature regimes. Opal is always found infilling voids in low-temperature regimes.”

morrie said:

diddly-squat said:

PM 2Ring said:

I can understand a bit of heat being involved in opal formation, but surely not enough to actually melt silica! I was under the impression that opal is amorphous hydrated silica, essentially a form of silica gel, so too much heat would tend to bake the water out of it and thus disrupt its structure, although I guess it could cope with wet heat.

Opal formation is a result of hydrothermal processes. Essentially mineral bearing hydrothermal solutions cool and precipitate out the minerals that form, in this instance, the opal.

Except Michael V just said:

“Darragh and Gaskin first discovered the structure of opal in the early 60’s, and developed a low-temperature model that explained the formation of both common and precious opal. The model must be pretty reasonable, because precious opal was first synthesised in the ’70’s.

I note here that opal is not found in high-temperature regimes. Opal is always found infilling voids in low-temperature regimes.”

MV’s and my comments are not in contradiction

>>No, I am not. I am saying the basin is 1000 m deep at that point. The margin of the basin is a long way away. It is not close by.<<

This is pure nit-picking! We are dealing with hot water directly from the Artesian Basin and Lightning Ridge is on the outer edge of the Basin, or where the water is being directed to the surface along fault lines, usually the result of land formation that to all rational thinking is the outer edge of the Basin.
———————————————————————————
>>You were the person asserting that a continuous capping of silcrete or similar was a necessary requirement of your model. I say that rarely occors, and also pointed out a well-known opal-bearing region where the silcrete is sporadic, usually isolated cobbles.<<

Well in that case you would be well aware that opal does not occur throughout a region, despite having the required sandstone. Just why do you think this is the case?
————————————————————————————————
>>Name-calling is rude and counterproductive. I object to that sort of behaviour
I have no problems with you using a well-defined term, or if there is none, to define one yourself. We are certainly going to find it dificcult to discuss this matter if we don’t have a common language. I mean, that’s how good communiction occurs – where all words are defined and their meanings are understood by all.<<

Well if you stopped your nit-picking, plus I’m the big geologist attitude, we might get along a lot better. I did describe the environmental conditions to you in some detail, but you decided not to see them. Hence I think you should be more objective.
——————————————————————————————————
>>You prosed that the silica melted. I merely pointed out silica’s melting temperature, and that that temperature would likely melt the entire enclosing rock mass. The injuection of that amount of heat would be seen as massive volcanism. We simply don’t see that during the opal-forming phase.

Again, please resist name-calling and name-calling by association. These discussion techniques are rude, quite hurtful and very disrespectful.<<

Yet another bit of nit-picking! The silica disolved, feel better now! Your actions I find equally disrespectful and rude. I spent two years visiting most of the main opal fields throughout Australia in 4 States. I studied the open cuts, went down mines, drilled a considerable number of holes and read whatever was published on the subject. So I think my opinion is highly relivant and based on actual investigation, not just reading the geological litriture.

There has been very little investigation into the formation of opal despite the people actually involved in the industry knowing the explanations given do not match the underground situation. You might not think my experience amounts to much, but I consider it a damn site more knowledgeable and instructive than the nit-picking reguritation of old hackneyed explanations.

morrie said:

diddly-squat said:

PM 2Ring said:

I can understand a bit of heat being involved in opal formation, but surely not enough to actually melt silica! I was under the impression that opal is amorphous hydrated silica, essentially a form of silica gel, so too much heat would tend to bake the water out of it and thus disrupt its structure, although I guess it could cope with wet heat.

Opal formation is a result of hydrothermal processes. Essentially mineral bearing hydrothermal solutions cool and precipitate out the minerals that form, in this instance, the opal.

Except Michael V just said:

“Darragh and Gaskin first discovered the structure of opal in the early 60’s, and developed a low-temperature model that explained the formation of both common and precious opal. The model must be pretty reasonable, because precious opal was first synthesised in the ’70’s.

I note here that opal is not found in high-temperature regimes. Opal is always found infilling voids in low-temperature regimes.”

Areas of hydrothermal activity are low-temperature environments.

Name calling and rudeness again.

My final response is that I mined opals at The Grawin (and surrounding fields) for 13 years before I studied geology. I have visited many other opal regions, but not mined in those places. One of my honours theses was on opal genesis. That in no way means that I know everything that could be known about opal genesis, nor does it imply that I had intended to make you feel in any way inferior. I apologise if that has happened.

Basically all I asked for was an ability to communicate using mutually agreed definitions. Science cannot go forward without that. Perhaps you meant “dissolve” when you said “melt”. However “melt” has a definition that is quite different to “dissolve”. I can only respond to what you write, based on standard definitions.

If you find that approach nit-picking, then we are never going to be able to communicate effectively.

Remember MV that PF is JW

I don’t care what religion he is.

PermeateFree said:

>>You proposed that the silica melted. I merely pointed out silica’s melting temperature, and that that temperature would likely melt the entire enclosing rock mass. The injection of that amount of heat would be seen as massive volcanism. We simply don’t see that during the opal-forming phase.
<<

Yet another bit of nit-picking! The silica dissolved, feel better now!

It’s not nit-picking. Your use of “melt” when you meant “dissolved” was a major cause of misunderstanding in this thread.

So thankyou for clarifying this point.

I don’t have many virtues, but when I am corrected, I thank the person who corrected me for teaching me something. They’ve taken time out to do me a favour.

dv said:

I don’t have many virtues, but when I am corrected, I thank the person who corrected me for teaching me something. They’ve taken time out to do me a favour.

I think you meant to type ‘any virtues’. No need to thank me. :-)

dv said:

I don’t have many virtues, but when I am corrected, I thank the person who corrected me for teaching me something. They’ve taken time out to do me a favour.

—-

You don’t have many virtues? WFMD

How long is a fishing line?

I think you meant to type ‘any virtues’. No need to thank me. :-)
——

But I must, I simply must.

How long is a fishing line?

—

Its mass divided by its linear density

Michael V said:

Name calling and rudeness again.

My final response is that I mined opals at The Grawin (and surrounding fields) for 13 years before I studied geology. I have visited many other opal regions, but not mined in those places. One of my honours theses was on opal genesis. That in no way means that I know everything that could be known about opal genesis, nor does it imply that I had intended to make you feel in any way inferior. I apologise if that has happened.

Basically all I asked for was an ability to communicate using mutually agreed definitions. Science cannot go forward without that. Perhaps you meant “dissolve” when you said “melt”. However “melt” has a definition that is quite different to “dissolve”. I can only respond to what you write, based on standard definitions.

If you find that approach nit-picking, then we are never going to be able to communicate effectively.

Quite right I don’t think we will. And I drilled a few holes around Grawin too, but after a three weeks moved off to the larger fields and then up into Queensland. To understand opal it is vital that you investigate a wide range of sites to appreciate the influence of past events has had its development and the different forms opal takes.

I think you should realise that you do not know everything and in some situation others might know more than you on some subjects. You use your qualifications and geological jargon as a means to subdue others and elevate yourself and today is not the first time you have attempted to do this with me. If you don’t want to converse with me, then that perfectly alright, but if you do please come with an open mind and not with preconceived attitudes.

tauto said:

Remember MV that PF is JW

Yes and I eat children too. So what!

PermeateFree said:

Michael V said:

Name calling and rudeness again.

My final response is that I mined opals at The Grawin (and surrounding fields) for 13 years before I studied geology. I have visited many other opal regions, but not mined in those places. One of my honours theses was on opal genesis. That in no way means that I know everything that could be known about opal genesis, nor does it imply that I had intended to make you feel in any way inferior. I apologise if that has happened.

Basically all I asked for was an ability to communicate using mutually agreed definitions. Science cannot go forward without that. Perhaps you meant “dissolve” when you said “melt”. However “melt” has a definition that is quite different to “dissolve”. I can only respond to what you write, based on standard definitions.

If you find that approach nit-picking, then we are never going to be able to communicate effectively.

Quite right I don’t think we will. And I drilled a few holes around Grawin too, but after a three weeks moved off to the larger fields and then up into Queensland. To understand opal it is vital that you investigate a wide range of sites to appreciate the influence of past events has had its development and the different forms opal takes.

I think you should realise that you do not know everything and in some situation others might know more than you on some subjects. You use your qualifications and geological jargon as a means to subdue others and elevate yourself and today is not the first time you have attempted to do this with me. If you don’t want to converse with me, then that perfectly alright, but if you do please come with an open mind and not with preconceived attitudes.

Now your just nitpicking…

poikilotherm said:

PermeateFree said:

Michael V said:

Name calling and rudeness again.

My final response is that I mined opals at The Grawin (and surrounding fields) for 13 years before I studied geology. I have visited many other opal regions, but not mined in those places. One of my honours theses was on opal genesis. That in no way means that I know everything that could be known about opal genesis, nor does it imply that I had intended to make you feel in any way inferior. I apologise if that has happened.

Basically all I asked for was an ability to communicate using mutually agreed definitions. Science cannot go forward without that. Perhaps you meant “dissolve” when you said “melt”. However “melt” has a definition that is quite different to “dissolve”. I can only respond to what you write, based on standard definitions.

If you find that approach nit-picking, then we are never going to be able to communicate effectively.

Quite right I don’t think we will. And I drilled a few holes around Grawin too, but after a three weeks moved off to the larger fields and then up into Queensland. To understand opal it is vital that you investigate a wide range of sites to appreciate the influence of past events has had its development and the different forms opal takes.

I think you should realise that you do not know everything and in some situation others might know more than you on some subjects. You use your qualifications and geological jargon as a means to subdue others and elevate yourself and today is not the first time you have attempted to do this with me. If you don’t want to converse with me, then that perfectly alright, but if you do please come with an open mind and not with preconceived attitudes.

Now your just nitpicking…

Well tell me how, am most interested to know.

PermeateFree said:

tauto said:

Remember MV that PF is JW

Yes and I eat children too. So what!

——

You have a record for being antagonistic to any that have a different view to you..

It seems that you can not engage in discussion for too long without resorting to derogatory language,

It seems to readers that you are a not a person to be trusted.

Which is a pity considering that you have gravitas in some of your opinions.

tauto said:

PermeateFree said:

tauto said:

Remember MV that PF is JW

Yes and I eat children too. So what!

——

Piss off you dumb bastard.

You have a record for being antagonistic to any that have a different view to you..

It seems that you can not engage in discussion for too long without resorting to derogatory language,

It seems to readers that you are a not a person to be trusted.

Which is a pity considering that you have gravitas in some of your opinions.

I was in a generous mood earlier in the day and with interest expressed last night about the subject, I thought I would inform you of a very poorly known subject, hopefully that some might find it interesting, but what do I find? The same small minded, self-righteous and suffocating obnoxious individuals doing what they can to undermine and otherwise trash my thread.

Well sorry for the French but fuck you people and you well know who you are. I tried to inform and produce a highly original insight that I doubt anyone else has ever investigated opal development to the extent I did. Well I am an original person and have done many unusual things in my life, which are very different from the stay-at-home intellectuals we have here, but I can assure you I shall not bore you with the deals in future.

You use your qualifications and geological jargon as a means to subdue others and elevate yourself.
—-

Hahahahahaha!

What a load of unmitigated, completely unsubstantiable tripe!

Please resolve your issues and resist trying to troll me.

PermeateFree said:

Well sorry for the French but fuck you people and you well know who you are

Ha ha come and say that to my face, little man.

Michael V said:

You use your qualifications and geological jargon as a means to subdue others and elevate yourself.
—-

Hahahahahaha!

What a load of unmitigated, completely unsubstantiable tripe!

Please resolve your issues and resist trying to troll me.

I bet the sun don’t shine where you are.

Spiny Norman said:

PermeateFree said:

Well sorry for the French but fuck you people and you well know who you are

Ha ha come and say that to my face, little man.

Well I’m not little, so you might need to rustle up a some courage yourself, or if you are like CS that will never happen.

PermeateFree said:

Spiny Norman said:

PermeateFree said:

Well sorry for the French but fuck you people and you well know who you are

Ha ha come and say that to my face, little man.

Well I’m not little, so you might need to rustle up a some courage yourself, or if you are like CS that will never happen.

I’ve thrown-up bigger things than you.

Spiny Norman said:

PermeateFree said:

Spiny Norman said:

Ha ha come and say that to my face, little man.

Well I’m not little, so you might need to rustle up a some courage yourself, or if you are like CS that will never happen.

I’ve thrown-up bigger things than you.

:))))

You know, it really buggers up the flow of discussion when everyone starts niggling over things that are not on the subject.

It makes catching up on the thread tedious and tends to cause me to skim rather than read the important bits.

I have a question. Under White Cliffs, where is the artesian water or the hydrothermal activity and if it isn’t there now, did it ever exist?

“The geological factors associated with opal formation continue to be the subject of research and active discussion by geologists, opal prospectors and miners.

Three main models for opal formation presently exist. Although the models have been put forward as stand-alone concepts, further research may show some linkages between them.”

As one who has been mining opal for 26 years, I’m inclined to accept that any two of the three may be more the reality and even the whole three, rather than any one stand alone.

The three are:
Weathering Model : In the Lightning Ridge opal fields, most opal is recovered from near the top of the various Finch clay facies lenses (opal dirt), immediately below the overlying portion of the Wallangulla Sandstone Member. Geological mapping of the opal fields has shown that the sandstone is thickest in areas that have produced large amounts of opal. Opal is rarely produced from areas in which the sandstone is thin or absent.

Syntectonic Model : This model proposes that opal formed from mineral-bearing waters rising towards the surface under pressure along fault and breccia pipes. Deformation of sandstone and claystone layers by large-scale, tectonic, geological processes caused water to be forced hydraulically into fractures and faults. As the water dissipated into areas of lower pressure, the opal was deposited as veins.

Microbe Model : The opal-bearing claystone commonly contains substantial amounts of fine, fossilised organic matter. Various types of microbe fossils, primarily aerobic (air-dependent) bacteria, have been identified within samples of opal from the Lightning Ridge area. Although none of these fossil organisms are visible to the naked eye, microscopic studies have shown them to be quite abundant.

Read in more detail: http://www.resources.nsw.gov.au/lightning-ridge/about-opal/formation-of-opal

roughbarked said:

You know, it really buggers up the flow of discussion when everyone starts niggling over things that are not on the subject.

It makes catching up on the thread tedious and tends to cause me to skim rather than read the important bits.

I have a question. Under White Cliffs, where is the artesian water or the hydrothermal activity and if it isn’t there now, did it ever exist?

It will be over 1500 ft below you. Hydrothermal activity could have happened anytime within the last 60 million years, but it would not have been a single event, but probably several over millions of years. I would think that in the past, good opal has been turned to potch by too much activity. To produce good opal requires very specific events, which might be too much or not enough, this is why opal is so rare. If it formed in simple conditions then we would be lining our roads with it.

roughbarked said:

“The geological factors associated with opal formation continue to be the subject of research and active discussion by geologists, opal prospectors and miners.

Three main models for opal formation presently exist. Although the models have been put forward as stand-alone concepts, further research may show some linkages between them.”

As one who has been mining opal for 26 years, I’m inclined to accept that any two of the three may be more the reality and even the whole three, rather than any one stand alone.

The three are:
Weathering Model : In the Lightning Ridge opal fields, most opal is recovered from near the top of the various Finch clay facies lenses (opal dirt), immediately below the overlying portion of the Wallangulla Sandstone Member. Geological mapping of the opal fields has shown that the sandstone is thickest in areas that have produced large amounts of opal. Opal is rarely produced from areas in which the sandstone is thin or absent.

Syntectonic Model : This model proposes that opal formed from mineral-bearing waters rising towards the surface under pressure along fault and breccia pipes. Deformation of sandstone and claystone layers by large-scale, tectonic, geological processes caused water to be forced hydraulically into fractures and faults. As the water dissipated into areas of lower pressure, the opal was deposited as veins.

Microbe Model : The opal-bearing claystone commonly contains substantial amounts of fine, fossilised organic matter. Various types of microbe fossils, primarily aerobic (air-dependent) bacteria, have been identified within samples of opal from the Lightning Ridge area. Although none of these fossil organisms are visible to the naked eye, microscopic studies have shown them to be quite abundant.

Read in more detail: http://www.resources.nsw.gov.au/lightning-ridge/about-opal/formation-of-opal

Sorry, but I don’t think it is any of those.

PermeateFree said:

roughbarked said:

You know, it really buggers up the flow of discussion when everyone starts niggling over things that are not on the subject.

It makes catching up on the thread tedious and tends to cause me to skim rather than read the important bits.

I have a question. Under White Cliffs, where is the artesian water or the hydrothermal activity and if it isn’t there now, did it ever exist?

It will be over 1500 ft below you. Hydrothermal activity could have happened anytime within the last 60 million years, but it would not have been a single event, but probably several over millions of years. I would think that in the past, good opal has been turned to potch by too much activity. To produce good opal requires very specific events, which might be too much or not enough, this is why opal is so rare. If it formed in simple conditions then we would be lining our roads with it.

How much opal mining have you done?

PermeateFree said:

roughbarked said:

“The geological factors associated with opal formation continue to be the subject of research and active discussion by geologists, opal prospectors and miners.

Three main models for opal formation presently exist. Although the models have been put forward as stand-alone concepts, further research may show some linkages between them.”

As one who has been mining opal for 26 years, I’m inclined to accept that any two of the three may be more the reality and even the whole three, rather than any one stand alone.

The three are:
Weathering Model : In the Lightning Ridge opal fields, most opal is recovered from near the top of the various Finch clay facies lenses (opal dirt), immediately below the overlying portion of the Wallangulla Sandstone Member. Geological mapping of the opal fields has shown that the sandstone is thickest in areas that have produced large amounts of opal. Opal is rarely produced from areas in which the sandstone is thin or absent.

Syntectonic Model : This model proposes that opal formed from mineral-bearing waters rising towards the surface under pressure along fault and breccia pipes. Deformation of sandstone and claystone layers by large-scale, tectonic, geological processes caused water to be forced hydraulically into fractures and faults. As the water dissipated into areas of lower pressure, the opal was deposited as veins.

Microbe Model : The opal-bearing claystone commonly contains substantial amounts of fine, fossilised organic matter. Various types of microbe fossils, primarily aerobic (air-dependent) bacteria, have been identified within samples of opal from the Lightning Ridge area. Although none of these fossil organisms are visible to the naked eye, microscopic studies have shown them to be quite abundant.

Read in more detail: http://www.resources.nsw.gov.au/lightning-ridge/about-opal/formation-of-opal

Sorry, but I don’t think it is any of those.

Well how do you explain the abundance of microorganisms found in opal? There’s a lot more about opal or understanding opal I’d like you to explain to me in detail as proof of your theory.

roughbarked said:

PermeateFree said:

roughbarked said:

You know, it really buggers up the flow of discussion when everyone starts niggling over things that are not on the subject.

It makes catching up on the thread tedious and tends to cause me to skim rather than read the important bits.

I have a question. Under White Cliffs, where is the artesian water or the hydrothermal activity and if it isn’t there now, did it ever exist?

It will be over 1500 ft below you. Hydrothermal activity could have happened anytime within the last 60 million years, but it would not have been a single event, but probably several over millions of years. I would think that in the past, good opal has been turned to potch by too much activity. To produce good opal requires very specific events, which might be too much or not enough, this is why opal is so rare. If it formed in simple conditions then we would be lining our roads with it.

How much opal mining have you done?

I have found opal, but my search was for the process it developed. I would look at the opal and think very pretty, but it did not attract me to actively mine for it.

I studied other peoples mines, underground and open cut. I also hired drillers to drill in certain places, both 9” and a metre diameter. You learn a great deal from drilling in the wrong place, although it definitely has its limits, but I would loved to own a 9” auger, then I would have solved so many of the still unanswered questions. Knowing how opal forms is one thing, finding it with a degree of certainly is another altogether.

PermeateFree said:

roughbarked said:

PermeateFree said:

It will be over 1500 ft below you. Hydrothermal activity could have happened anytime within the last 60 million years, but it would not have been a single event, but probably several over millions of years. I would think that in the past, good opal has been turned to potch by too much activity. To produce good opal requires very specific events, which might be too much or not enough, this is why opal is so rare. If it formed in simple conditions then we would be lining our roads with it.

How much opal mining have you done?

I have found opal, but my search was for the process it developed. I would look at the opal and think very pretty, but it did not attract me to actively mine for it.

I studied other peoples mines, underground and open cut. I also hired drillers to drill in certain places, both 9” and a metre diameter. You learn a great deal from drilling in the wrong place, although it definitely has its limits, but I would loved to own a 9” auger, then I would have solved so many of the still unanswered questions. Knowing how opal forms is one thing, finding it with a degree of certainly is another altogether.

I’ve spent a lot of time thinking about opal and know full well that precious opal is not easily found but that common opal pops up everywhere. Underground, I have led people who thought they were opal miners to where the opal is without fail. Above ground I can tell whether it could be opal bearing or not. I’ve never used a drill though I’d agree that it could be useful to narrow the search, I’ve seen a lot of drill holes that found nothing on some of the richest opal ground on earth.

roughbarked said:

PermeateFree said:

roughbarked said:

“The geological factors associated with opal formation continue to be the subject of research and active discussion by geologists, opal prospectors and miners.

Three main models for opal formation presently exist. Although the models have been put forward as stand-alone concepts, further research may show some linkages between them.”

As one who has been mining opal for 26 years, I’m inclined to accept that any two of the three may be more the reality and even the whole three, rather than any one stand alone.

The three are:
Weathering Model : In the Lightning Ridge opal fields, most opal is recovered from near the top of the various Finch clay facies lenses (opal dirt), immediately below the overlying portion of the Wallangulla Sandstone Member. Geological mapping of the opal fields has shown that the sandstone is thickest in areas that have produced large amounts of opal. Opal is rarely produced from areas in which the sandstone is thin or absent.

Syntectonic Model : This model proposes that opal formed from mineral-bearing waters rising towards the surface under pressure along fault and breccia pipes. Deformation of sandstone and claystone layers by large-scale, tectonic, geological processes caused water to be forced hydraulically into fractures and faults. As the water dissipated into areas of lower pressure, the opal was deposited as veins.

Microbe Model : The opal-bearing claystone commonly contains substantial amounts of fine, fossilised organic matter. Various types of microbe fossils, primarily aerobic (air-dependent) bacteria, have been identified within samples of opal from the Lightning Ridge area. Although none of these fossil organisms are visible to the naked eye, microscopic studies have shown them to be quite abundant.

Read in more detail: http://www.resources.nsw.gov.au/lightning-ridge/about-opal/formation-of-opal

Sorry, but I don’t think it is any of those.

Well how do you explain the abundance of microorganisms found in opal? There’s a lot more about opal or understanding opal I’d like you to explain to me in detail as proof of your theory.

I never studied the microbes, but I would imagine the broken sandstone with iron and other materials working their way down over millions of years would create some interesting micro-habitats. Microbes have been found over a kilometre deep in solid rock, so broken shallow opal fields should be a synch.

PermeateFree said:

roughbarked said:

PermeateFree said:

Sorry, but I don’t think it is any of those.

Well how do you explain the abundance of microorganisms found in opal? There’s a lot more about opal or understanding opal I’d like you to explain to me in detail as proof of your theory.

I never studied the microbes, but I would imagine the broken sandstone with iron and other materials working their way down over millions of years would create some interesting micro-habitats. Microbes have been found over a kilometre deep in solid rock, so broken shallow opal fields should be a synch.

I think you are missing the point by waffling about depths.

roughbarked said:

PermeateFree said:

roughbarked said:

How much opal mining have you done?

I have found opal, but my search was for the process it developed. I would look at the opal and think very pretty, but it did not attract me to actively mine for it.

I studied other peoples mines, underground and open cut. I also hired drillers to drill in certain places, both 9” and a metre diameter. You learn a great deal from drilling in the wrong place, although it definitely has its limits, but I would loved to own a 9” auger, then I would have solved so many of the still unanswered questions. Knowing how opal forms is one thing, finding it with a degree of certainly is another altogether.

I’ve spent a lot of time thinking about opal and know full well that precious opal is not easily found but that common opal pops up everywhere. Underground, I have led people who thought they were opal miners to where the opal is without fail. Above ground I can tell whether it could be opal bearing or not. I’ve never used a drill though I’d agree that it could be useful to narrow the search, I’ve seen a lot of drill holes that found nothing on some of the richest opal ground on earth.

You need to be able to detect blows and the minor slides to determine the best places to drill as the greatest concentration of opal is usually in those areas, but I agree with a single 9” hole you need to be lucky to strike opal, but what you bring up will also assist in deciding if more holes are warranted.

roughbarked said:

PermeateFree said:

roughbarked said:

Well how do you explain the abundance of microorganisms found in opal? There’s a lot more about opal or understanding opal I’d like you to explain to me in detail as proof of your theory.

I never studied the microbes, but I would imagine the broken sandstone with iron and other materials working their way down over millions of years would create some interesting micro-habitats. Microbes have been found over a kilometre deep in solid rock, so broken shallow opal fields should be a synch.

I think you are missing the point by waffling about depths.

What have I said that is so much waffle?

PermeateFree said:

roughbarked said:

PermeateFree said:

I have found opal, but my search was for the process it developed. I would look at the opal and think very pretty, but it did not attract me to actively mine for it.

I studied other peoples mines, underground and open cut. I also hired drillers to drill in certain places, both 9” and a metre diameter. You learn a great deal from drilling in the wrong place, although it definitely has its limits, but I would loved to own a 9” auger, then I would have solved so many of the still unanswered questions. Knowing how opal forms is one thing, finding it with a degree of certainly is another altogether.

I’ve spent a lot of time thinking about opal and know full well that precious opal is not easily found but that common opal pops up everywhere. Underground, I have led people who thought they were opal miners to where the opal is without fail. Above ground I can tell whether it could be opal bearing or not. I’ve never used a drill though I’d agree that it could be useful to narrow the search, I’ve seen a lot of drill holes that found nothing on some of the richest opal ground on earth.

You need to be able to detect blows and the minor slides to determine the best places to drill as the greatest concentration of opal is usually in those areas, but I agree with a single 9” hole you need to be lucky to strike opal, but what you bring up will also assist in deciding if more holes are warranted.

Yes. Finding a sandstone outcrop or any indication of faults and slippages, is important but each and every field differ somewhat around such things.

PermeateFree said:

roughbarked said:

PermeateFree said:

I never studied the microbes, but I would imagine the broken sandstone with iron and other materials working their way down over millions of years would create some interesting micro-habitats. Microbes have been found over a kilometre deep in solid rock, so broken shallow opal fields should be a synch.

I think you are missing the point by waffling about depths.

What have I said that is so much waffle?

Well, opal doesn’t need to form at great depth. Microorganisms don’t need to swim through rocks to get there. Need more?

roughbarked said:

PermeateFree said:

roughbarked said:

I’ve spent a lot of time thinking about opal and know full well that precious opal is not easily found but that common opal pops up everywhere. Underground, I have led people who thought they were opal miners to where the opal is without fail. Above ground I can tell whether it could be opal bearing or not. I’ve never used a drill though I’d agree that it could be useful to narrow the search, I’ve seen a lot of drill holes that found nothing on some of the richest opal ground on earth.

You need to be able to detect blows and the minor slides to determine the best places to drill as the greatest concentration of opal is usually in those areas, but I agree with a single 9” hole you need to be lucky to strike opal, but what you bring up will also assist in deciding if more holes are warranted.

Yes. Finding a sandstone outcrop or any indication of faults and slippages, is important but each and every field differ somewhat around such things.

In what way do they differ?

roughbarked said:

PermeateFree said:

roughbarked said:

I think you are missing the point by waffling about depths.

What have I said that is so much waffle?

Well, opal doesn’t need to form at great depth. Microorganisms don’t need to swim through rocks to get there. Need more?

Opal does not occur at depth and usually within 60 feet of the surface. I was merely pointing out that microbes are common underground and if the habitat comprises broken sandstone with iron and other materials, then the microbes would be many and diverse.

PermeateFree said:

roughbarked said:

PermeateFree said:

You need to be able to detect blows and the minor slides to determine the best places to drill as the greatest concentration of opal is usually in those areas, but I agree with a single 9” hole you need to be lucky to strike opal, but what you bring up will also assist in deciding if more holes are warranted.

Yes. Finding a sandstone outcrop or any indication of faults and slippages, is important but each and every field differ somewhat around such things.

In what way do they differ?

Much of the opal found at White Cliffs is under ironstone pebbles at the surface. The silcrete is usually below that. In most cases not visible to the eye..

PermeateFree said:

roughbarked said:

PermeateFree said:

What have I said that is so much waffle?

Well, opal doesn’t need to form at great depth. Microorganisms don’t need to swim through rocks to get there. Need more?

Opal does not occur at depth and usually within 60 feet of the surface. I was merely pointing out that microbes are common underground and if the habitat comprises broken sandstone with iron and other materials, then the microbes would be many and diverse.

Show me the broken sandstone and the ironstone.. in this image.

http://farm4.staticflickr.com/3691/9542372805_f61ff36450_c.jpg
= work by roughbarked, on Flickr

er, this image..

I’ve had a team of four geologists come down my ladders and look at opal ground. I’ve asked them relevant questions and they freely admitted that I knew 100% more about the geology of opal ground than they did. Which equates to the fact that they knew bugger all.

My sister-in-law and her husband are consulting geologists. Neither of them have been able to tell me much about opal at all.

So that makes six geologists I’ve queried, the latter two with masters degrees.. and yet no real answers.

In the scheme of things, opal geology isn’t that big…

dv said:

In the scheme of things, opal geology isn’t that big…

no. All of them could tell me heaps about gold etc.

roughbarked said:

PermeateFree said:

roughbarked said:

Yes. Finding a sandstone outcrop or any indication of faults and slippages, is important but each and every field differ somewhat around such things.

In what way do they differ?

Much of the opal found at White Cliffs is under ironstone pebbles at the surface. The silcrete is usually below that. In most cases not visible to the eye..

silcrete can form at various times and is not dependant upon a specific period, but must be there before the opal can be formed in order to create a cap and stop the release of pressure. To have it below the opal suggest the original cap has eroded away and it has formed since due to other non-opal forming thermal activity, or possibly low level activity like hot water running below the opal habitat that changed the local silica composition. From my investigations it requires several hydrothermal events to create the conditions suitable for opal formation.

I have been to many locations where insufficient activity had taken place and without the need for drilling I knew opal has not formed. In other areas, too much activity had taken place (around opal producing fields), but any opal formed would now be ruined, or not formed at all. Again not worth looking for opal there. The early miners knew all these indicators and in their own way knew the ways of opal well, although not how it was formed.

roughbarked said:

dv said:

In the scheme of things, opal geology isn’t that big…

no. All of them could tell me heaps about gold etc.

Yes

roughbarked said:

PermeateFree said:

roughbarked said:

Well, opal doesn’t need to form at great depth. Microorganisms don’t need to swim through rocks to get there. Need more?

Opal does not occur at depth and usually within 60 feet of the surface. I was merely pointing out that microbes are common underground and if the habitat comprises broken sandstone with iron and other materials, then the microbes would be many and diverse.

Show me the broken sandstone and the ironstone.. in this image.

http://farm4.staticflickr.com/3691/9542372805_f61ff36450_c.jpg
= work by roughbarked, on Flickr

I don’t think I have made it clear to you what I mean. The sandstone can be cracked and broken anywhere within the opal layer, it is just an indication of weathering and past events. There is no ironstone as such only the iron staining, no doubt produced by impurities and weathering.

roughbarked said:

I’ve had a team of four geologists come down my ladders and look at opal ground. I’ve asked them relevant questions and they freely admitted that I knew 100% more about the geology of opal ground than they did. Which equates to the fact that they knew bugger all.

My sister-in-law and her husband are consulting geologists. Neither of them have been able to tell me much about opal at all.

So that makes six geologists I’ve queried, the latter two with masters degrees.. and yet no real answers.

And your point is?

dv said:

In the scheme of things, opal geology isn’t that big…

More than you would think I wager.

PermeateFree said:

roughbarked said:

PermeateFree said:

In what way do they differ?

Much of the opal found at White Cliffs is under ironstone pebbles at the surface. The silcrete is usually below that. In most cases not visible to the eye..

silcrete can form at various times and is not dependant upon a specific period, but must be there before the opal can be formed in order to create a cap and stop the release of pressure. To have it below the opal suggest the original cap has eroded away and it has formed since due to other non-opal forming thermal activity, or possibly low level activity like hot water running below the opal habitat that changed the local silica composition. From my investigations it requires several hydrothermal events to create the conditions suitable for opal formation.

I have been to many locations where insufficient activity had taken place and without the need for drilling I knew opal has not formed. In other areas, too much activity had taken place (around opal producing fields), but any opal formed would now be ruined, or not formed at all. Again not worth looking for opal there. The early miners knew all these indicators and in their own way knew the ways of opal well, although not how it was formed.

It certainly takes several events. There are certainly large parts of the earth that one would not conceive opal to be. Not sure about ruination of opal by too much activity. I have my own theories about what constitutes ruined opal and all that but I’d like to hear more from you on that subject. Not formed at all would surely indicate not the right conditions but I doubt that it was overcooking that was responsible. The early miners were usually already miners. This gave them some insight into how things happened but by and large they shared information and thus the facts about where opal was found were generally common knowledge.

More than you would think I wager.

—

Okay, I am going to go out there and guess that the value of Australia’s opal exports are less than 1% of our iron ore exports…

PermeateFree said:

roughbarked said:

PermeateFree said:

Opal does not occur at depth and usually within 60 feet of the surface. I was merely pointing out that microbes are common underground and if the habitat comprises broken sandstone with iron and other materials, then the microbes would be many and diverse.

Show me the broken sandstone and the ironstone.. in this image.

http://farm4.staticflickr.com/3691/9542372805_f61ff36450_c.jpg
= work by roughbarked, on Flickr

I don’t think I have made it clear to you what I mean. The sandstone can be cracked and broken anywhere within the opal layer, it is just an indication of weathering and past events. There is no ironstone as such only the iron staining, no doubt produced by impurities and weathering.

I’m well aware of many things about opal and yes it is true that you need to include more clarity but I can read between the lines though it shouldn’t be necessary if you speak about mud with more clarity. “The opal layer”, is something you will need to clarify with me. True there exists only ironstone staining but then I’ve already pointed out that ironstone is common at the current eroded surface. It seems that weathering is one section of your model hypothesis of a sudden. I didn’t hear much on weathering earlier in your synopsis.

http://www.opalsdownunder.com.au/index.php?q=learn-about-opals/advanced/how-opal-formed-geology-opal

A Detailed Explanation

Occasionally, when conditions are ideal, spheres of silica, contained in silica-rich solutions in the earth form and settle under gravity in a void to form layers of silica spheres. The solution is believed to have a rate of deposition of approximately one centimetre thickness in five million years at a depth of forty metres. If the process allows spheres to reach uniform size, then precious opal commences to form. For precious opal the sphere size ranges from approximately 150 to 400 nanometres producing a play of colour by diffraction in the visible light range of 400 to 700 nanometres.

Each local opal field or occurrence must have contained voids or porosity of some sort to provide a site for opal deposition. In volcanic rocks and adjacent environments the opal appears to fill only vughs and cracks whereas in sedimentary rocks there are a variety of voids created by the weathering process. Leaching of carbonate from boulders, nodules, many different fossils, along with the existing cracks, open centres of ironstone nodules and horizontal seams provide a myriad of moulds ready for the deposition of secondary minerals such as opal….

The formation of Boulder Opal

The Boulder opal found in Queensland forms in a slightly different method to other types of opal, forming inside an ironstone concretion. The concretion was formed due to ionisation, from sedimentary deposition. By definition, they are ionised concretions of varying hardness with an approximate opal composition of SiO2at 28%, Fe2O3 + AL203 at 68% and H2O at 1% composition.

The opal forms in generally elongated or ellipsoidal ironstone concretions or boulders, from a few centimetres, to up to 3 m across. The boulders may be confined to one or more layers or randomly distributed through the weathered sandstone. Their composition ranges from sandstone types (a rim or crust of ferruginised sandstone surrounding a sandstone core) or ironstone types (composed almost entirely of iron oxides)…..

PermeateFree said:

roughbarked said:

I’ve had a team of four geologists come down my ladders and look at opal ground. I’ve asked them relevant questions and they freely admitted that I knew 100% more about the geology of opal ground than they did. Which equates to the fact that they knew bugger all.

My sister-in-law and her husband are consulting geologists. Neither of them have been able to tell me much about opal at all.

So that makes six geologists I’ve queried, the latter two with masters degrees.. and yet no real answers.

And your point is?

I would have thought that obvious.

dv said:

More than you would think I wager.

—

Okay, I am going to go out there and guess that the value of Australia’s opal exports are less than 1% of our iron ore exports…

Common opal has few known uses.

transition said:

http://www.opalsdownunder.com.au/index.php?q=learn-about-opals/advanced/how-opal-formed-geology-opal

A Detailed Explanation

You’ll find many such reports and many more besides. ie:

THE FORMATION OF PRECIOUS OPAL:
CLUES FROM THE OPALIZATION OF BONE
Benjamath PeWKLIanG, aLLan PRInG§ and joëL BRUGGeR
Department of Mineralogy, South Australian Museum, North Terrace, Adelaide, South Australia 5000,
and School of Earth & Environmental Sciences, Discipline of Geology & Geophysics,
University of Adelaide, Adelaide 5005, South Australia, Australia
aBstRact
The composition and microstructure of opalized saurian bones (Plesiosaur) from Andamooka, South Australia, have been
analyzed and compared to saurian bones that have been partially replaced by magnesian calcite from the same geological forma-
tion, north of Coober Pedy, South Australia. Powder X-ray-diffraction analyses show that the opalized bones are composed of
opal-AG and quartz. Major- and minor-element XRF analyses show that they are essentially pure SiO2 (88.59 to 92.69 wt%),
with minor amounts of Al2O3 (2.02 to 4.41 wt%) and H2O (3.36 to 4.23 wt%). No traces of biogenic apatite remain after opal-
ization. The opal is depleted in all trace elements relative to PAAS. During the formation of the opal, the coarser details of the
bone microstructure have been preserved down to the level of the individual osteons (scale of around 100 mm), but the central
canals and the boundary area have been enlarged and filled with chalcedony, which postdates opal formation. These chemical
and microstructural features are consistent with the opalization process being a secondary replacement after partial replacement
of the bone by magnesian calcite. They are also consistent with the opal forming first as a gel in the small cavities left by the
osteons, and the individual opal spheres growing as they settle within the gel. Changes in the viscosity of the gel provide a ready
explanation for the occurrence of color and potch banding in opals. The indication that opalization is a secondary process after
calcification on the Australian opal fields is consistent with a Tertiary age for formation.

roughbarked said:

PermeateFree said:

roughbarked said:

Much of the opal found at White Cliffs is under ironstone pebbles at the surface. The silcrete is usually below that. In most cases not visible to the eye..

silcrete can form at various times and is not dependant upon a specific period, but must be there before the opal can be formed in order to create a cap and stop the release of pressure. To have it below the opal suggest the original cap has eroded away and it has formed since due to other non-opal forming thermal activity, or possibly low level activity like hot water running below the opal habitat that changed the local silica composition. From my investigations it requires several hydrothermal events to create the conditions suitable for opal formation.

I have been to many locations where insufficient activity had taken place and without the need for drilling I knew opal has not formed. In other areas, too much activity had taken place (around opal producing fields), but any opal formed would now be ruined, or not formed at all. Again not worth looking for opal there. The early miners knew all these indicators and in their own way knew the ways of opal well, although not how it was formed.

It certainly takes several events. There are certainly large parts of the earth that one would not conceive opal to be. Not sure about ruination of opal by too much activity. I have my own theories about what constitutes ruined opal and all that but I’d like to hear more from you on that subject. Not formed at all would surely indicate not the right conditions but I doubt that it was overcooking that was responsible. The early miners were usually already miners. This gave them some insight into how things happened but by and large they shared information and thus the facts about where opal was found were generally common knowledge.

Precious opal is made up of tiny spheres that stack upon each other and between these spheres there are gaps with no opal. It is the arrangement of these spheres that produce the colour from reflected light. If with additional heating these gaps become contaminated with additional silica and the gaps filled, the light reflection changes and potch is the result. Potch I should add is also produced without ever forming precious opal.

You’ll find many reports..

Between 100 million and 97 million years ago, a vast sea that covered 60 per cent of Australia – from Coober Pedy in South Australia to the Gulf of Carpentaria in northern Australia – began retreating.

This drying out of Australia’s centre increased the acidity levels at shallow depth, releasing silica through the weathering of sandtone. Further weathering then lowered the acidity to a level at which precious opal can form in the silica-rich gel.

Central Australia is believed to be the only place on earth where acidic weathering of this scale has ever taken place, although similar conditions have been observed on the surface of Mars.

Non-precious opal deposits were discovered on the Red Planet by NASA in 2008.

“If you look at Mars and the Red Centre, they share similar characteristics,” says Patrice. “Similar rocks went through similar weathering processes, so potentially precious opals might exist there.”

Patrice says central Australia offers a “unique natural laboratory”, where researchers can study biological processes that could potentially be present on Mars.

Mike Snow, a minerals expert at the South Australian Museum, says the findings are compelling, and may well provide a glimpse into the landscape on Mars.

“The landscapes of Mars and the Centre both have large amounts of red oxidised iron,” says Mike. “This is part of the opal story.”

“Perhaps opal may well occur on Mars if it is similar to the Great Artesian Basin.”

dv said:

More than you would think I wager.

—

Okay, I am going to go out there and guess that the value of Australia’s opal exports are less than 1% of our iron ore exports…

No one knows my Lord, no one. To quote a distinguished contributor.

PermeateFree said:

roughbarked said:

PermeateFree said:

silcrete can form at various times and is not dependant upon a specific period, but must be there before the opal can be formed in order to create a cap and stop the release of pressure. To have it below the opal suggest the original cap has eroded away and it has formed since due to other non-opal forming thermal activity, or possibly low level activity like hot water running below the opal habitat that changed the local silica composition. From my investigations it requires several hydrothermal events to create the conditions suitable for opal formation.

I have been to many locations where insufficient activity had taken place and without the need for drilling I knew opal has not formed. In other areas, too much activity had taken place (around opal producing fields), but any opal formed would now be ruined, or not formed at all. Again not worth looking for opal there. The early miners knew all these indicators and in their own way knew the ways of opal well, although not how it was formed.

It certainly takes several events. There are certainly large parts of the earth that one would not conceive opal to be. Not sure about ruination of opal by too much activity. I have my own theories about what constitutes ruined opal and all that but I’d like to hear more from you on that subject. Not formed at all would surely indicate not the right conditions but I doubt that it was overcooking that was responsible. The early miners were usually already miners. This gave them some insight into how things happened but by and large they shared information and thus the facts about where opal was found were generally common knowledge.

Precious opal is made up of tiny spheres that stack upon each other and between these spheres there are gaps with no opal. It is the arrangement of these spheres that produce the colour from reflected light. If with additional heating these gaps become contaminated with additional silica and the gaps filled, the light reflection changes and potch is the result. Potch I should add is also produced without ever forming precious opal.

not seriously sciency enough. The molecular structure is either random higgledy piddly or.. evenly stacked. Gaps exist in both formations.
Opal forms in horizontal bands that are usually level. though some do look like somebody stirred the gel up and it settled instantly afterwards into a pattern that looks disturbed.. I can show photos if you wait until I take some. In many instances potch and colour are in separate bands. Other instances show potch with various inclusions of colour of different natures, mostly even patterns.

PermeateFree said:

dv said:

More than you would think I wager.

—

Okay, I am going to go out there and guess that the value of Australia’s opal exports are less than 1% of our iron ore exports…

No one knows my Lord, no one. To quote a distinguished contributor.

We have a poster known as My Lord?

Little is actually known about how much opal was mined and sold. Most sales have been very private affairs.

roughbarked said:

PermeateFree said:

roughbarked said:

Show me the broken sandstone and the ironstone.. in this image.

http://farm4.staticflickr.com/3691/9542372805_f61ff36450_c.jpg
= work by roughbarked, on Flickr

I don’t think I have made it clear to you what I mean. The sandstone can be cracked and broken anywhere within the opal layer, it is just an indication of weathering and past events. There is no ironstone as such only the iron staining, no doubt produced by impurities and weathering.

I’m well aware of many things about opal and yes it is true that you need to include more clarity but I can read between the lines though it shouldn’t be necessary if you speak about mud with more clarity. “The opal layer”, is something you will need to clarify with me. True there exists only ironstone staining but then I’ve already pointed out that ironstone is common at the current eroded surface. It seems that weathering is one section of your model hypothesis of a sudden. I didn’t hear much on weathering earlier in your synopsis.

Rb, I am getting a tired of your questions, you seem to have another agenda than a thirst for knowledge. It you want to learn something then stop all this crap.

>>…all this…

kemonstrating ones dnowledge.

roughbarked said:

I’ve had a team of four geologists come down my ladders and look at opal ground. I’ve asked them relevant questions and they freely admitted that I knew 100% more about the geology of opal ground than they did. Which equates to the fact that they knew bugger all.

My sister-in-law and her husband are consulting geologists. Neither of them have been able to tell me much about opal at all.

So that makes six geologists I’ve queried, the latter two with masters degrees.. and yet no real answers.

Have you read this paper, rb? I am not sure if it is one of the ones you linked last night.

http://www.earthbyte.org/Resources/Pdf/Rey_Opals_AJES_2013.pdf

Opalisation of the GAB, an Australian story with a Martian twist.

Australian Journal of Earth Sciences, July 2013

PermeateFree said:

Rb, I am getting a tired of your questions, you seem to have another agenda than a thirst for knowledge. It you want to learn something then stop all this crap.

Clearly along with the lack of clarity we can also surmise a lack of patience. You are incorrect about a lack of thirst for knowledge but if I am to study under you then you need to display claritty patiently. I am all ears if you are clear about exactly what you mean to say.

Earlier, you completely discounted weathering. Then later you dropped it in as if it was always there.

morrie said:

roughbarked said:

I’ve had a team of four geologists come down my ladders and look at opal ground. I’ve asked them relevant questions and they freely admitted that I knew 100% more about the geology of opal ground than they did. Which equates to the fact that they knew bugger all.

My sister-in-law and her husband are consulting geologists. Neither of them have been able to tell me much about opal at all.

So that makes six geologists I’ve queried, the latter two with masters degrees.. and yet no real answers.

Have you read this paper, rb? I am not sure if it is one of the ones you linked last night.

http://www.earthbyte.org/Resources/Pdf/Rey_Opals_AJES_2013.pdf

Opalisation of the GAB, an Australian story with a Martian twist.

Australian Journal of Earth Sciences, July 2013

Was reading this.. http://www.tandfonline.com/doi/pdf/10.1080/08120099.2013.784219

morrie said:

roughbarked said:

I’ve had a team of four geologists come down my ladders and look at opal ground. I’ve asked them relevant questions and they freely admitted that I knew 100% more about the geology of opal ground than they did. Which equates to the fact that they knew bugger all.

My sister-in-law and her husband are consulting geologists. Neither of them have been able to tell me much about opal at all.

So that makes six geologists I’ve queried, the latter two with masters degrees.. and yet no real answers.

Have you read this paper, rb? I am not sure if it is one of the ones you linked last night.

http://www.earthbyte.org/Resources/Pdf/Rey_Opals_AJES_2013.pdf

Opalisation of the GAB, an Australian story with a Martian twist.

Australian Journal of Earth Sciences, July 2013

Make that May 2013

roughbarked said:

morrie said:

roughbarked said:

I’ve had a team of four geologists come down my ladders and look at opal ground. I’ve asked them relevant questions and they freely admitted that I knew 100% more about the geology of opal ground than they did. Which equates to the fact that they knew bugger all.

My sister-in-law and her husband are consulting geologists. Neither of them have been able to tell me much about opal at all.

So that makes six geologists I’ve queried, the latter two with masters degrees.. and yet no real answers.

Have you read this paper, rb? I am not sure if it is one of the ones you linked last night.

http://www.earthbyte.org/Resources/Pdf/Rey_Opals_AJES_2013.pdf

Opalisation of the GAB, an Australian story with a Martian twist.

Australian Journal of Earth Sciences, July 2013

Was reading this.. http://www.tandfonline.com/doi/pdf/10.1080/08120099.2013.784219

Ah, same thing

roughbarked said:

PermeateFree said:

Rb, I am getting a tired of your questions, you seem to have another agenda than a thirst for knowledge. It you want to learn something then stop all this crap.

Clearly along with the lack of clarity we can also surmise a lack of patience. You are incorrect about a lack of thirst for knowledge but if I am to study under you then you need to display claritty patiently. I am all ears if you are clear about exactly what you mean to say.

Earlier, you completely discounted weathering. Then later you dropped it in as if it was always there.

That crap from you is an insult. I would think you are being coached by morrie, which fits like a glove. You are a fool rb, you don’t know when people are sincerely trying to help you. Anyway you have made your bed as they say.

PermeateFree said:

roughbarked said:

PermeateFree said:

Rb, I am getting a tired of your questions, you seem to have another agenda than a thirst for knowledge. It you want to learn something then stop all this crap.

Clearly along with the lack of clarity we can also surmise a lack of patience. You are incorrect about a lack of thirst for knowledge but if I am to study under you then you need to display claritty patiently. I am all ears if you are clear about exactly what you mean to say.

Earlier, you completely discounted weathering. Then later you dropped it in as if it was always there.

That crap from you is an insult. I would think you are being coached by morrie, which fits like a glove. You are a fool rb, you don’t know when people are sincerely trying to help you. Anyway you have made your bed as they say.

well, please sincerely show me how what you just said is trying to help me.

I was trying to help you explain to me how I was reading you.

roughbarked said:

PermeateFree said:

roughbarked said:

Clearly along with the lack of clarity we can also surmise a lack of patience. You are incorrect about a lack of thirst for knowledge but if I am to study under you then you need to display claritty patiently. I am all ears if you are clear about exactly what you mean to say.

Earlier, you completely discounted weathering. Then later you dropped it in as if it was always there.

That crap from you is an insult. I would think you are being coached by morrie, which fits like a glove. You are a fool rb, you don’t know when people are sincerely trying to help you. Anyway you have made your bed as they say.

well, please sincerely show me how what you just said is trying to help me.

I was trying to help you explain to me how I was reading you.

In fact my opal mines are open to anyone who feels qualified to show me what they believe is the case about many things that puzzle me. You are welcome to point to it and clear up the various shades of mud I see. That’s why I post pictures that are really taken with my camera.

roughbarked said:

PermeateFree said:

roughbarked said:

Clearly along with the lack of clarity we can also surmise a lack of patience. You are incorrect about a lack of thirst for knowledge but if I am to study under you then you need to display claritty patiently. I am all ears if you are clear about exactly what you mean to say.

Earlier, you completely discounted weathering. Then later you dropped it in as if it was always there.

That crap from you is an insult. I would think you are being coached by morrie, which fits like a glove. You are a fool rb, you don’t know when people are sincerely trying to help you. Anyway you have made your bed as they say.

well, please sincerely show me how what you just said is trying to help me.

I was trying to help you explain to me how I was reading you.

I was giving you pertinent information about how opal was formed and under what conditions, but you along with morrie and others thought you would have some sport with me. Well you have had your fun, but there will be no more. Had you held off a little longer rb and at least pretended to be interested I could have given you some very useful information, but you stuffed it. Too bad!

roughbarked said:

roughbarked said:

PermeateFree said:

That crap from you is an insult. I would think you are being coached by morrie, which fits like a glove. You are a fool rb, you don’t know when people are sincerely trying to help you. Anyway you have made your bed as they say.

well, please sincerely show me how what you just said is trying to help me.

I was trying to help you explain to me how I was reading you.

In fact my opal mines are open to anyone who feels qualified to show me what they believe is the case about many things that puzzle me. You are welcome to point to it and clear up the various shades of mud I see. That’s why I post pictures that are really taken with my camera.

Anyone who can look into your mind rb has more than their fair share of problems.

PermeateFree said:

I was giving you pertinent information about how opal was formed and under what conditions

I thank you, I was listening.
PermeateFree said:

but you along with morrie and others thought you would have some sport with me.

You totally misinterpret me. I am not in the same class as morrie and others in any way at all. Morrie has met me and I’m sure he has an entirely different opinion.
PermeateFree said:

That’ Well you have had your fun, but there will be no more. Had you held off a little longer rb and at least pretended to be interested I could have given you some very useful information, but you stuffed it. Too bad!

In my opinion, the latter is completely uncalled for. I am far more interested than your patience with me extends, may be a more accurate description.
One thing you can definitely be sure about is that I am not playing games with you. If you hear me make a joke, it will at least sound like a bad attempt at humour.

PermeateFree said:

roughbarked said:

roughbarked said:

well, please sincerely show me how what you just said is trying to help me.

I was trying to help you explain to me how I was reading you.

In fact my opal mines are open to anyone who feels qualified to show me what they believe is the case about many things that puzzle me. You are welcome to point to it and clear up the various shades of mud I see. That’s why I post pictures that are really taken with my camera.

Anyone who can look into your mind rb has more than their fair share of problems.

I’d be interested in the reactions of my masters if that was said in front of them. By masters, I do mean the men who I have been apprenticed to since 1975. They both happen to be master watchmakers, jewellers, and opal miners among many other talents. They can read me like a book and they do say “bullshit” when they feel the need to shut me up. However they usually do go on to explain why.

oops.. since 1970. 1975 was when my official apprenticeship ended. I am still their pupil and friend. We sit together in a dugout and discuss our shared pool of knowledge about opal often.

roughbarked said:

oops.. since 1970. 1975 was when my official apprenticeship ended. I am still their pupil and friend. We sit together in a dugout and discuss our shared pool of knowledge about opal often.

We would all be good listeners if you sat at our table.

Since this thread is everything about opal I’d like to show some pictures. Comments are welcome.

Sorry but the large pic was more dramatic if it loaded for you.

It is true that more than one opal exploration has been done by myself. None have yielded nothing or all have yielded something, whichever you’d prefer. Not all shafts were actually dug by myself but it is true that I have sunk new shafts.

Divine Angel said:

I’d like to know why Australia (almost) has the monopoly on opal mining. Why are there so many opals here?

I’d hope that if you read the thread carefully, that question could find answers.

in addition here is an answer to part of the question.

http://nhminsci.blogspot.com.au/2012/07/loving-ethiopian-opals.html

roughbarked said:

Nice…about how big are these bits?

kii said:

roughbarked said:

Nice…about how big are these bits?

The big bits are:
Red bit in foreground 3.5 cm by 2.5 cm by 5 mm thick. Full play of red with multicolour background. solid crystal.
The main large stone is 4.1 cm by 3 cm by 1.4 cm thick. Strong red thick bands in centre with green bands top and bottom.

The one on the left of the main large stone, is laying on side to show layering. It is 1.7 cm high, 1.6 cm wide and 3.3 cm long

You can also view other photos here. http://www.flickr.com/photos/67449903@N00/?details=1

http://geea.geoscienceworld.org/content/12/2/93.abstract

AUSTRALIAN SEDIMENTARY OPAL – WHY IS AUSTRALIA UNIQUE?
David Horton, Managing Director, Opal Horizon Limited
ABSTRACT
Australia currently produces about 95 per cent of the world’s precious opal from widely
scattered fields throughout central Australia. No other country on Earth has such an
abundance of this rare precious gemstone.
The sedimentary opal deposits of central Australia occur along generally flat-lying horizontal
layers within 30 metres of the earth’s surface. They are a product of a unique set of
geological events which occurred over a 100 million year period. These events can be
summarised as follows:
1. Between about 122 million years ago (Ma) and 91 Ma, central Australia was
covered by a vast shallow epicontinental sea. The sedimentary rocks which were
deposited in this sea were derived from volcanic rocks and were organic-rich.
These formed the principal host rocks for opal deposits in central Australia.
2. Following surface exposure through lowering of the sea level, these host rocks were
subject to a prolonged sub-tropical weathering regime until about 40 Ma. Central
Australia probably looked not unlike today’s Amazon Basin. During this time, the
water table was close to the surface and was acidic releasing silica and iron from
weathering of the host rocks.
3. The climate became more arid from about 40 Ma and, as a result, water table levels
gradually lowered and the groundwater became alkaline. Mild tectonism at 24 Ma
gave rise to subtle extremely long wavelength surface folds which facilitated both
lateral and vertical migration under arid conditions of the earlier-released silica.
Opal was preserved in the weathered profiles beneath the crests of the developing
surface folds as water tables here lowered more rapidly due to tectonic uplift.
Siliceous cap rocks discouraged erosion.
4. Over the last 10 million years, dissection and scarp erosion exposed the weathering
profiles containing the opal.
Geologists believe that the volume of gems that have been produced over the past 150
years in Australia is but a minute fraction of the amount yet to be discovered.
http://www.opalhorizon.com/Portals/0/Opal_DJ%20Horton.pdf

I want it said that I don’t believe everything I read. For example; on the love Ethiopian opal page he claims that Ethiopian opal bounces and that opal from other parts of the world including Australia don’t. That they smash when dropped on a hard surface.

Now that’s just bumkum because no science was properly presented. There is a difference in hardness of all opal. The molecular arrangement is a clue. Doesn’t matter where it comes from. Unless gem quality opal has been mistreated, it will be sound and can indeed bounce without shattering.

roughbarked said:

I want it said that I don’t believe everything I read. For example; on the love Ethiopian opal page he claims that Ethiopian opal bounces and that opal from other parts of the world including Australia don’t. That they smash when dropped on a hard surface.

Now that’s just bumkum because no science was properly presented. There is a difference in hardness of all opal. The molecular arrangement is a clue. Doesn’t matter where it comes from. Unless gem quality opal has been mistreated, it will be sound and can indeed bounce without shattering.

Reminds me of the bouncing cranberries ad gone wrong. Opals will be graded by height of bounce!

Riff-in-Thyme said:

roughbarked said:

I want it said that I don’t believe everything I read. For example; on the love Ethiopian opal page he claims that Ethiopian opal bounces and that opal from other parts of the world including Australia don’t. That they smash when dropped on a hard surface.

Now that’s just bumkum because no science was properly presented. There is a difference in hardness of all opal. The molecular arrangement is a clue. Doesn’t matter where it comes from. Unless gem quality opal has been mistreated, it will be sound and can indeed bounce without shattering.

Reminds me of the bouncing cranberries ad gone wrong. Opals will be graded by height of bounce!

Interesting. I hadn’t heard of the cranberry separator. It didn’t come up in my searching or patent office searching when I applied for a patent on a very similar device, with a few additional features and variations many years ago. The patent office did find a gravel separator though that worked on that principle, from 1956. That was enough to curtail the application.

Nice hole in the ground you have there rb, have you been working on it very long?

Do you think it will produce much more opal, or has it passed its best days?

PermeateFree said:

Nice hole in the ground you have there rb, have you been working on it very long?

Do you think it will produce much more opal, or has it passed its best days?

I’ve been on the same 50 m x 50 m claim for 26 years. The images span 3 shafts I’ve been investigating. The one I am in now was dropped down to approx 2 metres above the actual opal bearing level and a tunnel to another shaft exists but it is backfilled to the ceiling. I’ve been taking the floor out and have made quite a few new rooms in the building but the entire opal layer was untouched before I started on it. So yes. there is more years of work than I have life left.

roughbarked said:

PermeateFree said:

Nice hole in the ground you have there rb, have you been working on it very long?

Do you think it will produce much more opal, or has it passed its best days?

I’ve been on the same 50 m x 50 m claim for 26 years. The images span 3 shafts I’ve been investigating. The one I am in now was dropped down to approx 2 metres above the actual opal bearing level and a tunnel to another shaft exists but it is backfilled to the ceiling. I’ve been taking the floor out and have made quite a few new rooms in the building but the entire opal layer was untouched before I started on it. So yes. there is more years of work than I have life left.

You must have spent more time on it in the past than you do today. Do you think the main areas of opal production have been mined out now (presumably you must ).

PermeateFree said:

roughbarked said:

PermeateFree said:

Nice hole in the ground you have there rb, have you been working on it very long?

Do you think it will produce much more opal, or has it passed its best days?

I’ve been on the same 50 m x 50 m claim for 26 years. The images span 3 shafts I’ve been investigating. The one I am in now was dropped down to approx 2 metres above the actual opal bearing level and a tunnel to another shaft exists but it is backfilled to the ceiling. I’ve been taking the floor out and have made quite a few new rooms in the building but the entire opal layer was untouched before I started on it. So yes. there is more years of work than I have life left.

You must have spent more time on it in the past than you do today. Do you think the main areas of opal production have been mined out now (presumably you must ).

In the hole I am in.. the entire opal bearing area has not been dug. in the past two holes the area I dug out was also previously not dug. I’m working between shafts that were sunk by hand 150 years ago. Exactly 22 feet separates each shaft. They mainly dug from 10 to 15 feet. I’m taking out the 26 foot level.

roughbarked said:

PermeateFree said:

roughbarked said:

I’ve been on the same 50 m x 50 m claim for 26 years. The images span 3 shafts I’ve been investigating. The one I am in now was dropped down to approx 2 metres above the actual opal bearing level and a tunnel to another shaft exists but it is backfilled to the ceiling. I’ve been taking the floor out and have made quite a few new rooms in the building but the entire opal layer was untouched before I started on it. So yes. there is more years of work than I have life left.

You must have spent more time on it in the past than you do today. Do you think the main areas of opal production have been mined out now (presumably you must ).

In the hole I am in.. the entire opal bearing area has not been dug. in the past two holes the area I dug out was also previously not dug. I’m working between shafts that were sunk by hand 150 years ago. Exactly 22 feet separates each shaft. They mainly dug from 10 to 15 feet. I’m taking out the 26 foot level.

Don’t you know your main opal producing zones? A level where opal can be produced is one dimension, but there are areas within that level where the better deposits are more likely to be.

PermeateFree said:

roughbarked said:

PermeateFree said:

You must have spent more time on it in the past than you do today. Do you think the main areas of opal production have been mined out now (presumably you must ).

In the hole I am in.. the entire opal bearing area has not been dug. in the past two holes the area I dug out was also previously not dug. I’m working between shafts that were sunk by hand 150 years ago. Exactly 22 feet separates each shaft. They mainly dug from 10 to 15 feet. I’m taking out the 26 foot level.

Don’t you know your main opal producing zones? A level where opal can be produced is one dimension, but there are areas within that level where the better deposits are more likely to be.

Yes.. but it is all about removing the dirt to be able get to those places where the opal can be picked up with the fingers. Opal needs the overburdening pressure to be relieved before it can safely be collected. Other than in small dusty shards that is.

roughbarked said:

PermeateFree said:

roughbarked said:

In the hole I am in.. the entire opal bearing area has not been dug. in the past two holes the area I dug out was also previously not dug. I’m working between shafts that were sunk by hand 150 years ago. Exactly 22 feet separates each shaft. They mainly dug from 10 to 15 feet. I’m taking out the 26 foot level.

Don’t you know your main opal producing zones? A level where opal can be produced is one dimension, but there are areas within that level where the better deposits are more likely to be.

Yes.. but it is all about removing the dirt to be able get to those places where the opal can be picked up with the fingers. Opal needs the overburdening pressure to be relieved before it can safely be collected. Other than in small dusty shards that is.

The main producing zone of the ground I am working is ALL of the dirt (actually very hard rock) that exists from 0 to 26 feet, where I hit bottom dirt. Sometimes if a larger fault exists, the opal will run into the bottom dirt but otherwise it sits on top.

roughbarked said:

PermeateFree said:

roughbarked said:

In the hole I am in.. the entire opal bearing area has not been dug. in the past two holes the area I dug out was also previously not dug. I’m working between shafts that were sunk by hand 150 years ago. Exactly 22 feet separates each shaft. They mainly dug from 10 to 15 feet. I’m taking out the 26 foot level.

Don’t you know your main opal producing zones? A level where opal can be produced is one dimension, but there are areas within that level where the better deposits are more likely to be.

Yes.. but it is all about removing the dirt to be able get to those places where the opal can be picked up with the fingers. Opal needs the overburdening pressure to be relieved before it can safely be collected. Other than in small dusty shards that is.

Are you sure you understand what I am saying? That is being able to tunnel directly into the main opal bearing section, without having to remove the entire level.

PermeateFree said:

roughbarked said:

PermeateFree said:

Don’t you know your main opal producing zones? A level where opal can be produced is one dimension, but there are areas within that level where the better deposits are more likely to be.

Yes.. but it is all about removing the dirt to be able get to those places where the opal can be picked up with the fingers. Opal needs the overburdening pressure to be relieved before it can safely be collected. Other than in small dusty shards that is.

Are you sure you understand what I am saying? That is being able to tunnel directly into the main opal bearing section, without having to remove the entire level.

You have looked at the pictures haven’t you?

My original drive/tunnel was a metre by a metre crawl space. This went for six metres until I hit a serious fault. I then came back to the start of the tunnel and took the gloor out on a slope down another five metres at the far end.. then I took a section along the fault which was six by five by 3 metres.. all of it contained opal.. and the opal was also found on the down side of the slip.. in the floor of the sloping drive, after I had taken the main body. Then.. I bumped into another old shaft.. Which I cleaned out and found that they’d dug everything else other than the bit I had. Which meant there was very little still holding the shaft up, in both shafts. So I had to get out of there or any more digging would have buried me.

I do understand about tunneling to the likely spaces. That is what I am doing. In the old days they dropped a shaft and if it didn’t bottom on opal, they came up and dropped another shaft. it is the ground they didn’t look at that I am investigating. I’ve found opal from 50 mm to 2 metres from where they stopped looking.

roughbarked said:

PermeateFree said:

roughbarked said:

Yes.. but it is all about removing the dirt to be able get to those places where the opal can be picked up with the fingers. Opal needs the overburdening pressure to be relieved before it can safely be collected. Other than in small dusty shards that is.

Are you sure you understand what I am saying? That is being able to tunnel directly into the main opal bearing section, without having to remove the entire level.

You have looked at the pictures haven’t you?

My original drive/tunnel was a metre by a metre crawl space. This went for six metres until I hit a serious fault. I then came back to the start of the tunnel and took the gloor out on a slope down another five metres at the far end.. then I took a section along the fault which was six by five by 3 metres.. all of it contained opal.. and the opal was also found on the down side of the slip.. in the floor of the sloping drive, after I had taken the main body. Then.. I bumped into another old shaft.. Which I cleaned out and found that they’d dug everything else other than the bit I had. Which meant there was very little still holding the shaft up, in both shafts. So I had to get out of there or any more digging would have buried me.

So presumably you have removed all but a few bits and pieces from your mine? Why do you still mine there or is it just something to take a mate, then spend most of the time down at the pub telling grossly exaggerated opal mining stories?

roughbarked said:

I do understand about tunneling to the likely spaces. That is what I am doing. In the old days they dropped a shaft and if it didn’t bottom on opal, they came up and dropped another shaft. it is the ground they didn’t look at that I am investigating. I’ve found opal from 50 mm to 2 metres from where they stopped looking.

Sounds like they were the get rich quick hopefuls from town, not the knowledgeable old miners.

PermeateFree said:

roughbarked said:

PermeateFree said:

Are you sure you understand what I am saying? That is being able to tunnel directly into the main opal bearing section, without having to remove the entire level.

You have looked at the pictures haven’t you?

My original drive/tunnel was a metre by a metre crawl space. This went for six metres until I hit a serious fault. I then came back to the start of the tunnel and took the gloor out on a slope down another five metres at the far end.. then I took a section along the fault which was six by five by 3 metres.. all of it contained opal.. and the opal was also found on the down side of the slip.. in the floor of the sloping drive, after I had taken the main body. Then.. I bumped into another old shaft.. Which I cleaned out and found that they’d dug everything else other than the bit I had. Which meant there was very little still holding the shaft up, in both shafts. So I had to get out of there or any more digging would have buried me.

So presumably you have removed all but a few bits and pieces from your mine? Why do you still mine there or is it just something to take a mate, then spend most of the time down at the pub telling grossly exaggerated opal mining stories?

White Cliffs is nothing like Coober Pedy or Andamooka, Mintabie, Lightning Ridge, Winton, Yowah, Duck Creek and all those others. They are all different. The opal is not presented in the profile the same way in any of these fields… etc

roughbarked said:

PermeateFree said:

roughbarked said:

You have looked at the pictures haven’t you?

My original drive/tunnel was a metre by a metre crawl space. This went for six metres until I hit a serious fault. I then came back to the start of the tunnel and took the gloor out on a slope down another five metres at the far end.. then I took a section along the fault which was six by five by 3 metres.. all of it contained opal.. and the opal was also found on the down side of the slip.. in the floor of the sloping drive, after I had taken the main body. Then.. I bumped into another old shaft.. Which I cleaned out and found that they’d dug everything else other than the bit I had. Which meant there was very little still holding the shaft up, in both shafts. So I had to get out of there or any more digging would have buried me.

So presumably you have removed all but a few bits and pieces from your mine? Why do you still mine there or is it just something to take a mate, then spend most of the time down at the pub telling grossly exaggerated opal mining stories?

White Cliffs is nothing like Coober Pedy or Andamooka, Mintabie, Lightning Ridge, Winton, Yowah, Duck Creek and all those others. They are all different. The opal is not presented in the profile the same way in any of these fields… etc

I know rb, as I went to all bar one of those fields, but some things are common to all, apparently you have not noticed?

PermeateFree said:

roughbarked said:

I do understand about tunneling to the likely spaces. That is what I am doing. In the old days they dropped a shaft and if it didn’t bottom on opal, they came up and dropped another shaft. it is the ground they didn’t look at that I am investigating. I’ve found opal from 50 mm to 2 metres from where they stopped looking.

Sounds like they were the get rich quick hopefuls from town, not the knowledgeable old miners.

No. They were the people for whom the name “digger” was coined. The mostly went to Gallipoli and died there but not before they dug a lot of tunnels.

They knew about the economics of digging. They were paid sixpence a cubic foot for their work. and they had to wind the mullock up in a leather bucket on a rope, if they had one but first they had to find some trees to make a windlass from and kill a cow to get the hide to make the bucket and the bellows to use in a makeshift forge to re-sharpen their picks each night.. There are hundreds of thousands of pick strokes per cubic foot.

If they struck opal, the claim owners stopped work(and pay) and went down themselves to extract the opal.

PermeateFree said:

roughbarked said:

PermeateFree said:

So presumably you have removed all but a few bits and pieces from your mine? Why do you still mine there or is it just something to take a mate, then spend most of the time down at the pub telling grossly exaggerated opal mining stories?

White Cliffs is nothing like Coober Pedy or Andamooka, Mintabie, Lightning Ridge, Winton, Yowah, Duck Creek and all those others. They are all different. The opal is not presented in the profile the same way in any of these fields… etc

I know rb, as I went to all bar one of those fields, but some things are common to all, apparently you have not noticed?

Opal is common to all.. Yes, I have noticed but I’m open to anything you wish to tell me.

roughbarked said:

PermeateFree said:

roughbarked said:

White Cliffs is nothing like Coober Pedy or Andamooka, Mintabie, Lightning Ridge, Winton, Yowah, Duck Creek and all those others. They are all different. The opal is not presented in the profile the same way in any of these fields… etc

I know rb, as I went to all bar one of those fields, but some things are common to all, apparently you have not noticed?

Opal is common to all.. Yes, I have noticed but I’m open to anything you wish to tell me.

There is a lot more about opal fields than just opal. Surely you discovered this with all your mining experience rb?

I refer to the REAL old time miners who walked to the opal fields with little more than a pick and shovel. If these people did not learn quickly about the indicators of opal, then they did not survive long. These guys dug by hand and did not have petrol or electric motors to operate drilling and waste removal tools and certainly not blowers and tunnelling machines, so when they dug a hole they needed to be pretty sure they would find something. They learnt to tell by subtle observation the tell, tell signs of where the opal was and its potential size and if they thought their physical effort was unlikely to warrant the returns, they left it and went on to find a better spot.

roughbarked said:

PermeateFree said:

roughbarked said:

I do understand about tunneling to the likely spaces. That is what I am doing. In the old days they dropped a shaft and if it didn’t bottom on opal, they came up and dropped another shaft. it is the ground they didn’t look at that I am investigating. I’ve found opal from 50 mm to 2 metres from where they stopped looking.

Sounds like they were the get rich quick hopefuls from town, not the knowledgeable old miners.

No. They were the people for whom the name “digger” was coined. The mostly went to Gallipoli and died there but not before they dug a lot of tunnels.

They knew about the economics of digging. They were paid sixpence a cubic foot for their work. and they had to wind the mullock up in a leather bucket on a rope, if they had one but first they had to find some trees to make a windlass from and kill a cow to get the hide to make the bucket and the bellows to use in a makeshift forge to re-sharpen their picks each night.. There are hundreds of thousands of pick strokes per cubic foot.

If they struck opal, the claim owners stopped work(and pay) and went down themselves to extract the opal.

I did reply to this post but for some reason it was removed or did not appear. I repeat this is one of those grossly exaggerated stories passed around the pub and if you believe that, then the sky is the limit with such stories.

PermeateFree said:

roughbarked said:

PermeateFree said:

I know rb, as I went to all bar one of those fields, but some things are common to all, apparently you have not noticed?

Opal is common to all.. Yes, I have noticed but I’m open to anything you wish to tell me.

There is a lot more about opal fields than just opal. Surely you discovered this with all your mining experience rb?

I refer to the REAL old time miners who walked to the opal fields with little more than a pick and shovel. If these people did not learn quickly about the indicators of opal, then they did not survive long. These guys dug by hand and did not have petrol or electric motors to operate drilling and waste removal tools and certainly not blowers and tunnelling machines, so when they dug a hole they needed to be pretty sure they would find something. They learnt to tell by subtle observation the tell, tell signs of where the opal was and its potential size and if they thought their physical effort was unlikely to warrant the returns, they left it and went on to find a better spot.

Yes. That is clearly the case and the puzzle left behind for us all to solve. You perhaps misinterpret me. Yes.. I do need to actually find opal and actually sell the stuff. I’ve done the first, the second hasn’t happened yet. My main intention is as yours.. to look and learn how and why. If I live long enough.. I’ll take this experience to a field that actually produces opal that does sell for good money. In the meantime it is all about learning to understand the geology that surrounds the unique formation of pure crystal opal. Nobbies and Yowah nuts, boulder opal etc., are currently not what I am looking for but.. If I am aware of exactly what to look for, the same experience may be applied anywhere where opal may have formed.

White Cliffs is as unique as any other field but perhaps more so. It would appear to me to be the field that holds the link to the puzzle. If this is the field you haven’t visited, I am offering you a welcome card to come down and have a look.

PermeateFree said:

roughbarked said:

PermeateFree said:

Sounds like they were the get rich quick hopefuls from town, not the knowledgeable old miners.

No. They were the people for whom the name “digger” was coined. The mostly went to Gallipoli and died there but not before they dug a lot of tunnels.

They knew about the economics of digging. They were paid sixpence a cubic foot for their work. and they had to wind the mullock up in a leather bucket on a rope, if they had one but first they had to find some trees to make a windlass from and kill a cow to get the hide to make the bucket and the bellows to use in a makeshift forge to re-sharpen their picks each night.. There are hundreds of thousands of pick strokes per cubic foot.

If they struck opal, the claim owners stopped work(and pay) and went down themselves to extract the opal.

I did reply to this post but for some reason it was removed or did not appear. I repeat this is one of those grossly exaggerated stories passed around the pub and if you believe that, then the sky is the limit with such stories.

I never believe anything I hear or read, until I replicate it myself.

roughbarked said:

PermeateFree said:

roughbarked said:

Opal is common to all.. Yes, I have noticed but I’m open to anything you wish to tell me.

There is a lot more about opal fields than just opal. Surely you discovered this with all your mining experience rb?

I refer to the REAL old time miners who walked to the opal fields with little more than a pick and shovel. If these people did not learn quickly about the indicators of opal, then they did not survive long. These guys dug by hand and did not have petrol or electric motors to operate drilling and waste removal tools and certainly not blowers and tunnelling machines, so when they dug a hole they needed to be pretty sure they would find something. They learnt to tell by subtle observation the tell, tell signs of where the opal was and its potential size and if they thought their physical effort was unlikely to warrant the returns, they left it and went on to find a better spot.

Yes. That is clearly the case and the puzzle left behind for us all to solve. You perhaps misinterpret me. Yes.. I do need to actually find opal and actually sell the stuff. I’ve done the first, the second hasn’t happened yet. My main intention is as yours.. to look and learn how and why. If I live long enough.. I’ll take this experience to a field that actually produces opal that does sell for good money. In the meantime it is all about learning to understand the geology that surrounds the unique formation of pure crystal opal. Nobbies and Yowah nuts, boulder opal etc., are currently not what I am looking for but.. If I am aware of exactly what to look for, the same experience may be applied anywhere where opal may have formed.

White Cliffs is as unique as any other field but perhaps more so. It would appear to me to be the field that holds the link to the puzzle. If this is the field you haven’t visited, I am offering you a welcome card to come down and have a look.

I have been to White Cliffs and see no reason to return. I did complete my studies and even wrote a paper, but for an unforeseen situation did not publish it, nor have I any interest in doing so. If you knew anything about opal mining rb and was interested in finding opal, you would not be frigging around your hole after 26 years, you would be after something better. But lets be honest, you do not have a working mine other than a place to visit occasionally to have a little pick in the hope of finding something. That is fine, the vast majority of people in the opals fields do the same, however in future it might be more beneficial to listen to people who have studied the situation, as you might actually learn something of value.

PermeateFree said:

roughbarked said:

PermeateFree said:

There is a lot more about opal fields than just opal. Surely you discovered this with all your mining experience rb?

I refer to the REAL old time miners who walked to the opal fields with little more than a pick and shovel. If these people did not learn quickly about the indicators of opal, then they did not survive long. These guys dug by hand and did not have petrol or electric motors to operate drilling and waste removal tools and certainly not blowers and tunnelling machines, so when they dug a hole they needed to be pretty sure they would find something. They learnt to tell by subtle observation the tell, tell signs of where the opal was and its potential size and if they thought their physical effort was unlikely to warrant the returns, they left it and went on to find a better spot.

Yes. That is clearly the case and the puzzle left behind for us all to solve. You perhaps misinterpret me. Yes.. I do need to actually find opal and actually sell the stuff. I’ve done the first, the second hasn’t happened yet. My main intention is as yours.. to look and learn how and why. If I live long enough.. I’ll take this experience to a field that actually produces opal that does sell for good money. In the meantime it is all about learning to understand the geology that surrounds the unique formation of pure crystal opal. Nobbies and Yowah nuts, boulder opal etc., are currently not what I am looking for but.. If I am aware of exactly what to look for, the same experience may be applied anywhere where opal may have formed.

White Cliffs is as unique as any other field but perhaps more so. It would appear to me to be the field that holds the link to the puzzle. If this is the field you haven’t visited, I am offering you a welcome card to come down and have a look.

I have been to White Cliffs and see no reason to return. I did complete my studies and even wrote a paper, but for an unforeseen situation did not publish it, nor have I any interest in doing so. If you knew anything about opal mining rb and was interested in finding opal, you would not be frigging around your hole after 26 years, you would be after something better. But lets be honest, you do not have a working mine other than a place to visit occasionally to have a little pick in the hope of finding something. That is fine, the vast majority of people in the opals fields do the same, however in future it might be more beneficial to listen to people who have studied the situation, as you might actually learn something of value.

I’ve been listening all along.. All you have done is tell me that I’m not listening.
Nothing has been said about what I am supposed to have been hearing.

To access a mine’s potential is something every mining company does in order to plan the efficient removal of the resource. It was also for this reason that the early knowledgeable miners used before mining opal. Now days people go down with power driven tools and aimlessly hack away in the unlikely hope of finding something of value. They rarely do and are even less likely to learn anything that would help them do so more profitably.

And rb, I was giving you information, but you preferred to be the smart-alec and follow the prompting of others. Had you been more interested and less manipulated by these people, I would have given you a great deal more, but you chose to mock me for short-term notoriety. I think you sought advice from the wrong people, but I could be wrong as they might have secretly researched opal formation too, but I doubt it.

PermeateFree said:

To access a mine’s potential is something every mining company does in order to plan the efficient removal of the resource. It was also for this reason that the early knowledgeable miners used before mining opal. Now days people go down with power driven tools and aimlessly hack away in the unlikely hope of finding something of value. They rarely do and are even less likely to learn anything that would help them do so more profitably.

And rb, I was giving you information, but you preferred to be the smart-alec and follow the prompting of others. Had you been more interested and less manipulated by these people, I would have given you a great deal more, but you chose to mock me for short-term notoriety. I think you sought advice from the wrong people, but I could be wrong as they might have secretly researched opal formation too, but I doubt it.

You are misapprehending me. totally.

roughbarked said:

PermeateFree said:

To access a mine’s potential is something every mining company does in order to plan the efficient removal of the resource. It was also for this reason that the early knowledgeable miners used before mining opal. Now days people go down with power driven tools and aimlessly hack away in the unlikely hope of finding something of value. They rarely do and are even less likely to learn anything that would help them do so more profitably.

And rb, I was giving you information, but you preferred to be the smart-alec and follow the prompting of others. Had you been more interested and less manipulated by these people, I would have given you a great deal more, but you chose to mock me for short-term notoriety. I think you sought advice from the wrong people, but I could be wrong as they might have secretly researched opal formation too, but I doubt it.

You are misapprehending me. totally.

The early miners did not spend years digging holes in hope of finding opal. They knew the most likely areas and would dig it out in realitively short time. This suggests to me that if you are still mining the same small area after 26 years, then you do not know how to access the potential of it.

I spent 2 years non-stop studying this aspect to reach the same understanding as the early miners. We both used observation, but I backed mine up with science, which you and others chose to mock at every opportunity. New ideas and ways of looking at things are very fragile and don’t deserve this sort of treatment, but there again, how many here do real science and are not like the failed small-time opal miners down the pub?

PermeateFree said:

roughbarked said:

PermeateFree said:

To access a mine’s potential is something every mining company does in order to plan the efficient removal of the resource. It was also for this reason that the early knowledgeable miners used before mining opal. Now days people go down with power driven tools and aimlessly hack away in the unlikely hope of finding something of value. They rarely do and are even less likely to learn anything that would help them do so more profitably.

And rb, I was giving you information, but you preferred to be the smart-alec and follow the prompting of others. Had you been more interested and less manipulated by these people, I would have given you a great deal more, but you chose to mock me for short-term notoriety. I think you sought advice from the wrong people, but I could be wrong as they might have secretly researched opal formation too, but I doubt it.

You are misapprehending me. totally.

The early miners did not spend years digging holes in hope of finding opal. They knew the most likely areas and would dig it out in realitively short time. This suggests to me that if you are still mining the same small area after 26 years, then you do not know how to access the potential of it.

I spent 2 years non-stop studying this aspect to reach the same understanding as the early miners. We both used observation, but I backed mine up with science, which you and others chose to mock at every opportunity. New ideas and ways of looking at things are very fragile and don’t deserve this sort of treatment, but there again, how many here do real science and are not like the failed small-time opal miners down the pub?

Since I have been misapprehended I don’t see myself as under arrest.

Look, if you don’t want to tell me. Why not simply say so and leave it at that?

I won’t be offended.

It should perhaps be pointed out that The place I’ve spent a couple of weeks per year in for 26 years is completely altered. There are no natural formations to observe on the surface. Without fail take any old shaft and use a tape measure. There will be a hole every 22 feet in any direction and they are all 22 feet from each other. they all dug to set levels of 2,4,6 8,10,12, feet or they didn’t. Most all stopped at around 18 or 20 feet or they dug all the ground on any level where opal stuck out of the wall or they didn’t. It is fairly simple. The ground is all rich, in small pockets. Traces are everywhere. Yes, if they found it, they took it. Yes, in all opal fields and patches and pockets the same conditions exist and it is these conditions that lead to the finding of the mother lode or the king stone. That’s why they were called gougers because they turned this way and that. Is also why many traces are left in the ground untouched.

There is nothing wrong with me treasuring the pieces they left behind as not worth the effort. I’m not using a pick other than to break up the lumps my jackhammer leaves.

roughbarked said:

It should perhaps be pointed out that The place I’ve spent a couple of weeks per year in for 26 years is completely altered. There are no natural formations to observe on the surface. Without fail take any old shaft and use a tape measure. There will be a hole every 22 feet in any direction and they are all 22 feet from each other. they all dug to set levels of 2,4,6 8,10,12, feet or they didn’t. Most all stopped at around 18 or 20 feet or they dug all the ground on any level where opal stuck out of the wall or they didn’t. It is fairly simple. The ground is all rich, in small pockets. Traces are everywhere. Yes, if they found it, they took it. Yes, in all opal fields and patches and pockets the same conditions exist and it is these conditions that lead to the finding of the mother lode or the king stone. That’s why they were called gougers because they turned this way and that. Is also why many traces are left in the ground untouched.

There is nothing wrong with me treasuring the pieces they left behind as not worth the effort. I’m not using a pick other than to break up the lumps my jackhammer leaves.

>>From: roughbarked

ID: 375065

Subject: re: August chatting

Carmen_Sandiego said:
Hey Roughy, you are arguing with Jack, remember. He can (and will) keep this all week if you let him.

It is OK, I can walk away any time I like, he’ll still be there when I get back.<<

:))))

PermeateFree said:

roughbarked said:

It should perhaps be pointed out that The place I’ve spent a couple of weeks per year in for 26 years is completely altered. There are no natural formations to observe on the surface. Without fail take any old shaft and use a tape measure. There will be a hole every 22 feet in any direction and they are all 22 feet from each other. they all dug to set levels of 2,4,6 8,10,12, feet or they didn’t. Most all stopped at around 18 or 20 feet or they dug all the ground on any level where opal stuck out of the wall or they didn’t. It is fairly simple. The ground is all rich, in small pockets. Traces are everywhere. Yes, if they found it, they took it. Yes, in all opal fields and patches and pockets the same conditions exist and it is these conditions that lead to the finding of the mother lode or the king stone. That’s why they were called gougers because they turned this way and that. Is also why many traces are left in the ground untouched.

There is nothing wrong with me treasuring the pieces they left behind as not worth the effort. I’m not using a pick other than to break up the lumps my jackhammer leaves.

>>From: roughbarked

ID: 375065

Subject: re: August chatting

Carmen_Sandiego said:
Hey Roughy, you are arguing with Jack, remember. He can (and will) keep this all week if you let him.

It is OK, I can walk away any time I like, he’ll still be there when I get back.<<

:))))

well blow me down, you are here. ;)

CrazyNeutrino said:

Ethiopian Welo Opal New gem found looks like the ocean in rock

PermeateFree said:

roughbarked said:

PermeateFree said:

There is very little opal in that piece, but mostly a clear potch with many impurities. This type of gem is quite common in the boulder opal of Queensland, where it is commonly referred to as sand-shot opal, although the piece shown looks to be of a good size and the natural beauty taken into account. Mostly little value is placed upon it, except when something can be made of it.

Sandshot is one thing.
http://forums.opalauctions.com/viewtopic.php?f=12&t=3559
http://www.mindat.org/mesg-11-197665.html

Impurities or inclusions are not uncommon, especially those within a boulder or nodule. I have some large pieces of silica with dendrites, which are a common occurrence and no connection with opal. I know several sites where this can be found around Norseman and eastwards, 200 km north of Esperance. Hydrothermal activity was however also an important feature in its formation.

http://www.jtv.com/library/ethiopian-opal-gia.html
Inclusions.

One sample (no. 1100) contained elongated, cylindrical inclusions measuring approximately 800 μm × 1 cm (figure 17). Their surface was very irregular. EDS showed that these “tubes” were filled with silica, which may correspond to chalcedony.The outside surface of the inclusions also consisted of silica. They appeared more difficult to polish than the host opal.

Dispersed micro-inclusions of black, opaque crystals were abundant in some samples (in particular,no. 1113). EDS analyses revealed iron and sulfur, which suggests they were pyrite (pyrite usuallyappears black in such small dimensions).

Some of the rough opal samples were outlined by a thin layer (less than 0.1 mm thick) of black, opaque minerals. These were identified by EDS asbarium-manganese oxides (probably hollandite) and native carbon (probably graphitic carbon). Also present in such layers were micrometer-sized crystals that were identified by EDS as titanium oxides(probably rutile). In rare instances, the black minerals were included in the body of the opal, filling fissures or forming dendrite.

I saw that pic pop up on my fb feed this morning.

Divine Angel said:

I saw that pic pop up on my fb feed this morning.

yes, it is out there in many locations.

A whole set of images from different viewpoints of the same “aquarium” opal. Someone is clearly trying to ramp the price of potch up.
http://www.mymodernmet.com/profiles/blogs/opal-butte-crystal

PermeateFree said:

morrie said:

Are you suggesting that limestone is dissolved by upwelling hot water?

Why, are you suggesting it is dissolved by seeping water?

Hot water gushing to the surface that could run for decades will certainly push out a lot of material and also wash it away. bit difficult to imagine how seepage could do the same but still form a cavity.

Now perhaps the OP really wants us to discuss the aspect of opal formation. As indeed throughout the thread he has expressed disappointment that we(the readers) don’t seem to get the point. I’ve been painted as a bonehead. Indeed I am interested in bones.
As for cavities. These do not necessarily have to have been labeled as a requirement of the actual process of opal formation. It is highly possible and indeed known to be the case that cavities may pre-exist the formation of the opal itself and that opal in-fills them during formation. Opal is indeed different in formations between known deposits, though quite clearly common factors do persist.

There is a possibility of good blues?

^ it is actually simply a one handed shot of dirty fingers.

roughbarked said:

There is a possibility of good blues?

Blues Run the Game

The Rev Dodgson said:

Blues Run the Game

:)

its only one piece.
It may be correct that it is all I will get and that even If I do explore all the area left unexplored by the original miners, it could still be fruitless hard manual labour.
The reason I’m digging here is that others did the same in the late 1890’s/early 1900’s. I am aware of the restrictions they faced and many of the reasons why they left such ground unexplored. It has been a steep learning curve trying to envisage from the surface and from underground, just where are the spots they left to dig still existing. It isn’t like I want to dig up the whole thing by hand. I don’t possess an excavator and as to this point in time, there are still restrictions upon using heavy machinery on this site.

roughbarked said:

PermeateFree said:

morrie said:

Are you suggesting that limestone is dissolved by upwelling hot water?

Why, are you suggesting it is dissolved by seeping water?

Hot water gushing to the surface that could run for decades will certainly push out a lot of material and also wash it away. bit difficult to imagine how seepage could do the same but still form a cavity.

Now perhaps the OP really wants us to discuss the aspect of opal formation. As indeed throughout the thread he has expressed disappointment that we(the readers) don’t seem to get the point. I’ve been painted as a bonehead. Indeed I am interested in bones.
As for cavities. These do not necessarily have to have been labeled as a requirement of the actual process of opal formation. It is highly possible and indeed known to be the case that cavities may pre-exist the formation of the opal itself and that opal in-fills them during formation. Opal is indeed different in formations between known deposits, though quite clearly common factors do persist.

You answer one post with one that is completely unrelated and as such is pointless.

PermeateFree said:

roughbarked said:

PermeateFree said:

Why, are you suggesting it is dissolved by seeping water?

Hot water gushing to the surface that could run for decades will certainly push out a lot of material and also wash it away. bit difficult to imagine how seepage could do the same but still form a cavity.

Now perhaps the OP really wants us to discuss the aspect of opal formation. As indeed throughout the thread he has expressed disappointment that we(the readers) don’t seem to get the point. I’ve been painted as a bonehead. Indeed I am interested in bones.
As for cavities. These do not necessarily have to have been labeled as a requirement of the actual process of opal formation. It is highly possible and indeed known to be the case that cavities may pre-exist the formation of the opal itself and that opal in-fills them during formation. Opal is indeed different in formations between known deposits, though quite clearly common factors do persist.

You answer one post with one that is completely unrelated and as such is pointless.

As is the original post. What precisely, is your point?

roughbarked said:

PermeateFree said:

roughbarked said:

Now perhaps the OP really wants us to discuss the aspect of opal formation. As indeed throughout the thread he has expressed disappointment that we(the readers) don’t seem to get the point. I’ve been painted as a bonehead. Indeed I am interested in bones.
As for cavities. These do not necessarily have to have been labeled as a requirement of the actual process of opal formation. It is highly possible and indeed known to be the case that cavities may pre-exist the formation of the opal itself and that opal in-fills them during formation. Opal is indeed different in formations between known deposits, though quite clearly common factors do persist.

You answer one post with one that is completely unrelated and as such is pointless.

As is the original post. What precisely, is your point?

Well, the post to which I was replying was about hydrothermal activity through limestone on the Nullarbor and had nothing to do with small cavities where opal sometimes accumulates. You had this information and produced some of it in your last post on the subject. So what is your point and what are you trying to prove?

PermeateFree said:

roughbarked said:

PermeateFree said:

You answer one post with one that is completely unrelated and as such is pointless.

As is the original post. What precisely, is your point?

Well, the post to which I was replying was about hydrothermal activity through limestone on the Nullarbor and had nothing to do with small cavities where opal sometimes accumulates. You had this information and produced some of it in your last post on the subject. So what is your point and what are you trying to prove?

I’m simply inquiring what the hydrothermal activity through limestone has to do with opal formation. Considering that this thread is titled; all about opal.

roughbarked said:

PermeateFree said:

roughbarked said:

As is the original post. What precisely, is your point?

Well, the post to which I was replying was about hydrothermal activity through limestone on the Nullarbor and had nothing to do with small cavities where opal sometimes accumulates. You had this information and produced some of it in your last post on the subject. So what is your point and what are you trying to prove?

I’m simply inquiring what the hydrothermal activity through limestone has to do with opal formation. Considering that this thread is titled; all about opal.

Geeze I’m am getting really sick of having to answer your stupid questions. Why don’t you just go back to where you cherry-picked your post and investigate.

PermeateFree said:

roughbarked said:

PermeateFree said:

Well, the post to which I was replying was about hydrothermal activity through limestone on the Nullarbor and had nothing to do with small cavities where opal sometimes accumulates. You had this information and produced some of it in your last post on the subject. So what is your point and what are you trying to prove?

I’m simply inquiring what the hydrothermal activity through limestone has to do with opal formation. Considering that this thread is titled; all about opal.

Geeze I’m am getting really sick of having to answer your stupid questions. Why don’t you just go back to where you cherry-picked your post and investigate.

PermeateFree said:

These two studies, have been recycled in most publications ever since, which basically considers opal is formed by water seeping down to slowly dissolve the silica that later collects in underground cavities. This sounds good, but from talking to experienced miners on most Australian opal fields, very few believe this to be the case, as it does not match the facts underground.

I’ve read it and I’ve read it but I’m still waiting for you to actually show me why you say the above. Where are the references?
What do you mean?

PermeateFree said:

roughbarked said:

PermeateFree said:

Well, the post to which I was replying was about hydrothermal activity through limestone on the Nullarbor and had nothing to do with small cavities where opal sometimes accumulates. You had this information and produced some of it in your last post on the subject. So what is your point and what are you trying to prove?

I’m simply inquiring what the hydrothermal activity through limestone has to do with opal formation. Considering that this thread is titled; all about opal.

Geeze I’m am getting really sick of having to answer your stupid questions. Why don’t you just go back to where you cherry-picked your post and investigate.

PermeateFree said:

These two studies, have been recycled in most publications ever since, which basically considers opal is formed by water seeping down to slowly dissolve the silica that later collects in underground cavities. This sounds good, but from talking to experienced miners on most Australian opal fields, very few believe this to be the case, as it does not match the facts underground.

I’ve read it and I’ve read it but I’m still waiting for you to actually show me why you say the above. Where are the references?
What do you mean?

roughbarked said:

PermeateFree said:

roughbarked said:

Geeze I’m am getting really sick of having to answer your stupid questions. Why don’t you just go back to where you cherry-picked your post and investigate.

PermeateFree said:

These two studies, have been recycled in most publications ever since, which basically considers opal is formed by water seeping down to slowly dissolve the silica that later collects in underground cavities. This sounds good, but from talking to experienced miners on most Australian opal fields, very few believe this to be the case, as it does not match the facts underground.

I’ve read it and I’ve read it but I’m still waiting for you to actually show me why you say the above. Where are the references?
What do you mean?

I don’t get the context here..

Could you two start again if you mind terribly?

Ian said:

roughbarked said:

PermeateFree said:

I’ve read it and I’ve read it but I’m still waiting for you to actually show me why you say the above. Where are the references?
What do you mean?

I don’t get the context here..

Could you two start again if you mind terribly?

I’m actually asking him to finish the starting..

he asked for additions to something that had nothing provided to speculate upon.. and you all know that it is my bent to try speculation on almost anything, without any basis.

roughbarked said:

Ian said:

roughbarked said:

I don’t get the context here..

Could you two start again if you mind terribly?

I’m actually asking him to finish the starting..

he asked for additions to something that had nothing provided to speculate upon.. and you all know that it is my bent to try speculation on almost anything, without any basis.

Aahaammm

Ian said:

roughbarked said:

Ian said:

I don’t get the context here..

Could you two start again if you mind terribly?

I’m actually asking him to finish the starting..

he asked for additions to something that had nothing provided to speculate upon.. and you all know that it is my bent to try speculation on almost anything, without any basis.

Aahaammm

Which is exactly why I was wondering why you needed to begin again.

either this starting point gets towards closure or it doesn’t.

roughbarked said:

PermeateFree said:

roughbarked said:

Geeze I’m am getting really sick of having to answer your stupid questions. Why don’t you just go back to where you cherry-picked your post and investigate.

PermeateFree said:

These two studies, have been recycled in most publications ever since, which basically considers opal is formed by water seeping down to slowly dissolve the silica that later collects in underground cavities. This sounds good, but from talking to experienced miners on most Australian opal fields, very few believe this to be the case, as it does not match the facts underground.

I’ve read it and I’ve read it but I’m still waiting for you to actually show me why you say the above. Where are the references?
What do you mean?

What you quote me saying is not my opinion but the common belief of what happens, so why should I explain it further to you? Quite frankly rb I don’t care whether you accept what I say or not, your opinion is of no interest to me.

PermeateFree said:

roughbarked said:

PermeateFree said:

PermeateFree said:

These two studies, have been recycled in most publications ever since, which basically considers opal is formed by water seeping down to slowly dissolve the silica that later collects in underground cavities. This sounds good, but from talking to experienced miners on most Australian opal fields, very few believe this to be the case, as it does not match the facts underground.

I’ve read it and I’ve read it but I’m still waiting for you to actually show me why you say the above. Where are the references?
What do you mean?

What you quote me saying is not my opinion but the common belief of what happens, so why should I explain it further to you? Quite frankly rb I don’t care whether you accept what I say or not, your opinion is of no interest to me.

Common belief rarely coincides with actual factual evidence.

Do you really believe that I do not look at any opal trace in any other way to that of other prospectors?

Ian said:

roughbarked said:

PermeateFree said:

I’ve read it and I’ve read it but I’m still waiting for you to actually show me why you say the above. Where are the references?
What do you mean?

The problem is rb is cherry-picking posts of mine and placing them into a different context.

I don’t get the context here..

Could you two start again if you mind terribly?

roughbarked said:

Ian said:

roughbarked said:

I don’t get the context here..

Could you two start again if you mind terribly?

I’m actually asking him to finish the starting..

he asked for additions to something that had nothing provided to speculate upon.. and you all know that it is my bent to try speculation on almost anything, without any basis.

Does anyone know what this is about?

roughbarked said:

Ian said:

roughbarked said:

I’m actually asking him to finish the starting..

he asked for additions to something that had nothing provided to speculate upon.. and you all know that it is my bent to try speculation on almost anything, without any basis.

Aahaammm

Which is exactly why I was wondering why you needed to begin again.

either this starting point gets towards closure or it doesn’t.

Or more likely going nowhere.

PermeateFree said:

Ian said:

roughbarked said:

The problem is rb is cherry-picking posts of mine and placing them into a different context.

I don’t get the context here..

Could you two start again if you mind terribly?

as I said, I’m waiting for you.

How as an opal prospector, how can I answer your statements if you never finish them?

roughbarked said:

PermeateFree said:

roughbarked said:

I’ve read it and I’ve read it but I’m still waiting for you to actually show me why you say the above. Where are the references?
What do you mean?

What you quote me saying is not my opinion but the common belief of what happens, so why should I explain it further to you? Quite frankly rb I don’t care whether you accept what I say or not, your opinion is of no interest to me.

Common belief rarely coincides with actual factual evidence.

Do you really believe that I do not look at any opal trace in any other way to that of other prospectors?

I have no idea what you are on about and I doubt if you do either. So why not go to bed or do something else?

PermeateFree said:

roughbarked said:

Ian said:

Aahaammm

Which is exactly why I was wondering why you needed to begin again.

either this starting point gets towards closure or it doesn’t.

Or more likely going nowhere.

Take it away Jack.

PermeateFree said:

roughbarked said:

PermeateFree said:

What you quote me saying is not my opinion but the common belief of what happens, so why should I explain it further to you? Quite frankly rb I don’t care whether you accept what I say or not, your opinion is of no interest to me.

Common belief rarely coincides with actual factual evidence.

Do you really believe that I do not look at any opal trace in any other way to that of other prospectors?

I have no idea what you are on about and I doubt if you do either. So why not go to bed or do something else?

You do have some good suggestions. Sadly they relate only to the time of night.

PermeateFree said:

roughbarked said:

Ian said:

I don’t get the context here..

Could you two start again if you mind terribly?

I’m actually asking him to finish the starting..

he asked for additions to something that had nothing provided to speculate upon.. and you all know that it is my bent to try speculation on almost anything, without any basis.

Does anyone know what this is about?

I know a really good to finish it..

Just drop the word c*nt a couple of times

:)

Ian said:

PermeateFree said:

roughbarked said:

I’m actually asking him to finish the starting..

he asked for additions to something that had nothing provided to speculate upon.. and you all know that it is my bent to try speculation on almost anything, without any basis.

Does anyone know what this is about?

I know a really good to finish it..

Just drop the word c*nt a couple of times

:)

it is not my mission to emulate others.

roughbarked said:

it is not my mission to emulate others.

Yes. That dv is a sly one!

I find it strange that that word is such a powerful taboo.. Fuck knows Derek and Clive did it to death in the 70s.

It’s only 4 letters.. a short ugly sound.

As someone in the intro to Conversations says, “Words have power.”

I suppose every underdone culture has to have its powerful taboo hex words.

Ian said:

I find it strange that that word is such a powerful taboo.. Fuck knows Derek and Clive did it to death in the 70s.

It’s only 4 letters.. a short ugly sound.

As someone in the intro to Conversations says, “Words have power.”

I suppose every underdone culture has to have its powerful taboo hex words.

that particular word is derogatory to the person you use the word against and all women everywhere. It’s a gender specific word that is used to be nasty and vile. Plus, it doesn’t make anyone look very smart.

Plus, we are adults who should be able to debate and argue without introducing personal insults.. if I want to listen to crass language I’ll go to one of the other gazillion forums out there where people don’t seem to care how others view their behaviour.

Arts said:

Ian said:

I find it strange that that word is such a powerful taboo.. Fuck knows Derek and Clive did it to death in the 70s.

It’s only 4 letters.. a short ugly sound.

As someone in the intro to Conversations says, “Words have power.”

I suppose every underdone culture has to have its powerful taboo hex words.

that particular word is derogatory to the person you use the word against and all women everywhere. It’s a gender specific word that is used to be nasty and vile. Plus, it doesn’t make anyone look very smart.

Plus, we are adults who should be able to debate and argue without introducing personal insults.. if I want to listen to crass language I’ll go to one of the other gazillion forums out there where people don’t seem to care how others view their behaviour.

I think Brooke is the only one who uses it here

A person from Wyoming asked me what I knew about opal in Wyoming as he is an amateur rockhound. A quick search revealed this. http://wy-opal.blogspot.com.au/