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I love all this 
Most interesting indeed.
I believe there is a little misunderstanding between what was being said though?
Lefty when goldierocks was talking about
"In Victoria and NSW it is not strictly that wood is buried in silica-rich material ejected from volcanoes (although you are correctly quoting this old geological idea that used to dominate in that science, but no longer - although some geos still think that). It is more that the wood gets buried in old river gravels and sands, then lavas fill the old valleys and cover the gravels"
I believe he was getting at the fact that the volcanic ash and lava flow are normally not responsible for preserving much of the wood we find. A lot of the wood was already buried in sand, gravel and mud, from being downed in floods and buried or stumps near the edge of banks being buried as the course of the water way has changed.
From my understanding there is opal associated with the volcanics in Australia but it is generally common opal or potch, whereas you both have said, all the precious opal fields seem to be in sedimentary ground.
Something i must ask though, you said:
"Eastern Australia is more complex again, as we had this as well up until about Cretaceous times. However most of the volcanoes of younger age in eastern Australia are thought to be "hot spot" related by many (not all) geos, not subduction"
I am still learning all this so i may it a bit wrong, but I thought ti was a mix of subduction and hot spot volcanism? Or am i misunderstanding you?
From my understanding we know that there was subduction from accretionary wedges and with that continental arcs and back arcs as do we know of the hot spot volcanism because of the evidence left of the shield volcanoes and the like?
Most interesting indeed.I believe there is a little misunderstanding between what was being said though?
Lefty when goldierocks was talking about
"In Victoria and NSW it is not strictly that wood is buried in silica-rich material ejected from volcanoes (although you are correctly quoting this old geological idea that used to dominate in that science, but no longer - although some geos still think that). It is more that the wood gets buried in old river gravels and sands, then lavas fill the old valleys and cover the gravels"
I believe he was getting at the fact that the volcanic ash and lava flow are normally not responsible for preserving much of the wood we find. A lot of the wood was already buried in sand, gravel and mud, from being downed in floods and buried or stumps near the edge of banks being buried as the course of the water way has changed.
From my understanding there is opal associated with the volcanics in Australia but it is generally common opal or potch, whereas you both have said, all the precious opal fields seem to be in sedimentary ground.
Something i must ask though, you said:
"Eastern Australia is more complex again, as we had this as well up until about Cretaceous times. However most of the volcanoes of younger age in eastern Australia are thought to be "hot spot" related by many (not all) geos, not subduction"
I am still learning all this so i may it a bit wrong, but I thought ti was a mix of subduction and hot spot volcanism? Or am i misunderstanding you?
From my understanding we know that there was subduction from accretionary wedges and with that continental arcs and back arcs as do we know of the hot spot volcanism because of the evidence left of the shield volcanoes and the like?
[=shivan]I love all this Most interesting indeed.
I believe there is a little misunderstanding between what was being said though?
Lefty when goldierocks was talking about
"In Victoria and NSW it is not strictly that wood is buried in silica-rich material ejected from volcanoes (although you are correctly quoting this old geological idea that used to dominate in that science, but no longer - although some geos still think that). It is more that the wood gets buried in old river gravels and sands, then lavas fill the old valleys and cover the gravels"
I believe he was getting at the fact that the volcanic ash and lava flow are normally not responsible for preserving much of the wood we find. A lot of the wood was already buried in sand, gravel and mud, from being downed in floods and buried or stumps near the edge of banks being buried as the course of the water way has changed.
From my understanding there is opal associated with the volcanics in Australia but it is generally common opal or potch, whereas you both have said, all the precious opal fields seem to be in sedimentary ground.
Essentially correct - the wood was already in the gravel. But the lavas covered the gravel and helped prevent the gravels being rapidly washed away. But we were also talking about water with silica then moving through the gravel and replacing the wood with silica to give silicified "petrified" wood.
Something i must ask though, you said:
"Eastern Australia is more complex again, as we had this as well up until about Cretaceous times. However most of the volcanoes of younger age in eastern Australia are thought to be "hot spot" related by many (not all) geos, not subduction"
I am still learning all this so i may it a bit wrong, but I thought ti was a mix of subduction and hot spot volcanism? Or am i misunderstanding you?
From my understanding we know that there was subduction from accretionary wedges and with that continental arcs and back arcs as do we know of the hot spot volcanism because of the evidence left of the shield volcanoes and the like?
No, most younger volcanoes are probably hot spot (although there is no complete consensus on this). The subduction was Cambrian to Devonian from Tasmania to NSW, Devonian to about Jurassic ir Early Cretaceous north of that. However in the Cretaceous the eastern Australian subduction zone (New Caledonia) became separated from Australia as the Tasman Sea opened and it moved away to the east. This meant that all the subduction activity east of the Tasman Sea continued as before but was now quite isolated from Australia. However Australia was now moving north as it separated from Antarctica and crossing over the stationery (and more deeply-based) hot spot - which formed a linear zone of volcanoes. The earliest were sometime around 100 My ago from memory and erupted in North Queensland, which was still far south of its present position. As Australia moved north the underlying hot spot did not move, so later eruptions were the Glasshouse Mountains, which then moved north, later the Warrumbungles, which then moved north, then the Mt Macedon -Woodend area of Victoria, perhaps Victoria's best sapphire locality (much younger than 30 My from memory, which moved north, until it was still active around Mt Gambier to a few thousand years ago (with fluid magma still present slightly further south around Bass Strait).
Hot Spot and subduction volcanism are very different mechanisms. Hot Spots are like a cylindrical rising magma column from deep in the mantle, perhaps as deep as the mantle-core boundary - magmas are very mafic (like basalt), low in water and often erupt quietly at surface, such as in Hawaii, Tristan de Cunha, Iceland or much of eastern Australia in the Tertiary (unless they are high in mantle carbon dioxide in which case they can be explosive but very small and localised - eg diamond-bearing kimberlites).
In subduction zones, the downgoing slab dehydrates only a few hundred km down and its water rises, lowering the melting point of the mantle above the downgoing plate which then melts and produces lavas higher in silica (andesite, dacite, rhyolite and only subordinate basalt), high in water and volatiles, which rise to surface and explosively erupt (eg Mt St Helens, Taupo NZ, Chile) - they tend to form linear chains, but in this case the volcanoes along the chain are all forming simultaneously, not sequentially.
You can see here the two parallel belts above a suduction zone - one of big silica-rich volcanoes above the trench, one further inland from the coast that is typically more basaltic (think Taupo versus Auckland that I mentioned before).
Here is the modern ocean floor:
You can see two linear belts of volcanoes - the Aleutian islands have a subduction zone south of them, and have silica-rich andesites and rhyolites erupting from volcanoes throughout their length. The Hawiaian islands only have active volcanoes above the hot spot below the Big Island (Hawaaii itself) - volcanoes west of it are dead but originally formed in the position of Hawaaii, but the sea floor crust moved them successively westward. In fact the Emperor seamounts on their continuation but trending more NW also originally each formed in the position of Hawaaii - the reason for the dog-leg bend is that the ocean floor changed direction from NW in the past to more W as it is now.
Most interesting indeed.I believe there is a little misunderstanding between what was being said though?
Lefty when goldierocks was talking about
"In Victoria and NSW it is not strictly that wood is buried in silica-rich material ejected from volcanoes (although you are correctly quoting this old geological idea that used to dominate in that science, but no longer - although some geos still think that). It is more that the wood gets buried in old river gravels and sands, then lavas fill the old valleys and cover the gravels"
I believe he was getting at the fact that the volcanic ash and lava flow are normally not responsible for preserving much of the wood we find. A lot of the wood was already buried in sand, gravel and mud, from being downed in floods and buried or stumps near the edge of banks being buried as the course of the water way has changed.
From my understanding there is opal associated with the volcanics in Australia but it is generally common opal or potch, whereas you both have said, all the precious opal fields seem to be in sedimentary ground.
Essentially correct - the wood was already in the gravel. But the lavas covered the gravel and helped prevent the gravels being rapidly washed away. But we were also talking about water with silica then moving through the gravel and replacing the wood with silica to give silicified "petrified" wood.
Something i must ask though, you said:
"Eastern Australia is more complex again, as we had this as well up until about Cretaceous times. However most of the volcanoes of younger age in eastern Australia are thought to be "hot spot" related by many (not all) geos, not subduction"
I am still learning all this so i may it a bit wrong, but I thought ti was a mix of subduction and hot spot volcanism? Or am i misunderstanding you?
From my understanding we know that there was subduction from accretionary wedges and with that continental arcs and back arcs as do we know of the hot spot volcanism because of the evidence left of the shield volcanoes and the like?
No, most younger volcanoes are probably hot spot (although there is no complete consensus on this). The subduction was Cambrian to Devonian from Tasmania to NSW, Devonian to about Jurassic ir Early Cretaceous north of that. However in the Cretaceous the eastern Australian subduction zone (New Caledonia) became separated from Australia as the Tasman Sea opened and it moved away to the east. This meant that all the subduction activity east of the Tasman Sea continued as before but was now quite isolated from Australia. However Australia was now moving north as it separated from Antarctica and crossing over the stationery (and more deeply-based) hot spot - which formed a linear zone of volcanoes. The earliest were sometime around 100 My ago from memory and erupted in North Queensland, which was still far south of its present position. As Australia moved north the underlying hot spot did not move, so later eruptions were the Glasshouse Mountains, which then moved north, later the Warrumbungles, which then moved north, then the Mt Macedon -Woodend area of Victoria, perhaps Victoria's best sapphire locality (much younger than 30 My from memory, which moved north, until it was still active around Mt Gambier to a few thousand years ago (with fluid magma still present slightly further south around Bass Strait).
Hot Spot and subduction volcanism are very different mechanisms. Hot Spots are like a cylindrical rising magma column from deep in the mantle, perhaps as deep as the mantle-core boundary - magmas are very mafic (like basalt), low in water and often erupt quietly at surface, such as in Hawaii, Tristan de Cunha, Iceland or much of eastern Australia in the Tertiary (unless they are high in mantle carbon dioxide in which case they can be explosive but very small and localised - eg diamond-bearing kimberlites).
In subduction zones, the downgoing slab dehydrates only a few hundred km down and its water rises, lowering the melting point of the mantle above the downgoing plate which then melts and produces lavas higher in silica (andesite, dacite, rhyolite and only subordinate basalt), high in water and volatiles, which rise to surface and explosively erupt (eg Mt St Helens, Taupo NZ, Chile) - they tend to form linear chains, but in this case the volcanoes along the chain are all forming simultaneously, not sequentially.
You can see here the two parallel belts above a suduction zone - one of big silica-rich volcanoes above the trench, one further inland from the coast that is typically more basaltic (think Taupo versus Auckland that I mentioned before).
Here is the modern ocean floor:
You can see two linear belts of volcanoes - the Aleutian islands have a subduction zone south of them, and have silica-rich andesites and rhyolites erupting from volcanoes throughout their length. The Hawiaian islands only have active volcanoes above the hot spot below the Big Island (Hawaaii itself) - volcanoes west of it are dead but originally formed in the position of Hawaaii, but the sea floor crust moved them successively westward. In fact the Emperor seamounts on their continuation but trending more NW also originally each formed in the position of Hawaaii - the reason for the dog-leg bend is that the ocean floor changed direction from NW in the past to more W as it is now.
My guess about the Fitzroy River region that Lefty was referring to was that it was in the northern Biloela Basin, between the Dee Range and Gagango Range. I showed a map earlier of the Biloela Basin that shows basalt outcropping at its northern and southern ends, but also underlying the basin between at depth (it has been intersected in boreholes). However there are other areas of basalt outcrop, as at Biloela itself (note the smallest patch of basalt flow with Tertiary sediments preserved beneath it, the situation I have been describing).
As for Mt Hay:
As for Mt Hay:
Here is the present-day situation, now that the eastern part of Australia is separated from NZ by the Tasman Sea, and Australia from Antarctica by the Southern Ocean. Compare it with my previous map. "Zealandia" was previously part of the Australian mainland - it is now mainly below sea level and no longer subaerial except for what we know as New Zealand and islands like New Caledonia (when sea levels drop, as they were only 10,000 years ago, New Zealand becomes a small continent in its own right, which includes New Caledonia and other islands - at that time Port Phillip Bay was a dry plain, and the aborigines could walk from New Guinea to Hobart without getting their feet wet).
New Zealand was a flat plain until 800,000 years ago - the Alps formed since. The aborigines arrived only 50,000 years ago, but humans were living in Africa already perhaps 200,000 years ago - the Bushmen (KhoiSan).
The green stars represent areas of Jurassic basalt that were originally next to each other. The subduction zone is no longer the island of New Caledonia as it was in the Cretaceous when Zealandia was part of Australia, on the eastern margin of "Zealandia". Instead it is now the black thick line east of the North Island of New Zealand (just east of the northern green star).
New Zealand was a flat plain until 800,000 years ago - the Alps formed since. The aborigines arrived only 50,000 years ago, but humans were living in Africa already perhaps 200,000 years ago - the Bushmen (KhoiSan).
The green stars represent areas of Jurassic basalt that were originally next to each other. The subduction zone is no longer the island of New Caledonia as it was in the Cretaceous when Zealandia was part of Australia, on the eastern margin of "Zealandia". Instead it is now the black thick line east of the North Island of New Zealand (just east of the northern green star).
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Cheers for that Goldirocks - some great info there! Had things been different when I was leaving high school, I might well have made geology a serious undertaking. I have a mate who has a geology degree but has never worked in the field - he walked out of uni into a previous mining bust before this one and no one was looking for geologists so he had to change tack and by the time things picked up again in that area he was already committed to something else.
Are you and your mates on gas exploration?
Did you look at the pictures I posted of the wood in the other thread? What are your thoughts? I didn't think we were likely to see the formation of banded agate with quartz crystal centres in the middle of a piece of pet wood without related thermal activity. Perhaps the wood was already fossilized and the hollows and cracks were later filled by hot silica-saturated water at the time of the eruptions. Is there such a thing as "cold" agate formation?
Yes, this is the region the material in the photograph originates from. The other material I mentioned comes from localities some distance (hundreds of kms) to the south and west of that map.
Are you and your mates on gas exploration?
Did you look at the pictures I posted of the wood in the other thread? What are your thoughts? I didn't think we were likely to see the formation of banded agate with quartz crystal centres in the middle of a piece of pet wood without related thermal activity. Perhaps the wood was already fossilized and the hollows and cracks were later filled by hot silica-saturated water at the time of the eruptions. Is there such a thing as "cold" agate formation?
Yes, this is the region the material in the photograph originates from. The other material I mentioned comes from localities some distance (hundreds of kms) to the south and west of that map.
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My father worked on many construction projects in the area in the 60's and 70's. An engineer told him that when they built the wall of the Callide dam near Biloela, small sapphires were found in the ground samples from where the footings of the wall were to go in.
Just outside Bilo is an interesting place called Mount Scoria.
If you going to attempt the climb to the top to look at the basalt columns then you need to be fit or crazy - the loose scree just keeps sliding under your feet and it's one hard slog up the side to the top.
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Petrified wood ain't petrified wood?
I have to agree with Lefty regarding the chalcedinized petrified wood he finds in Queensland, and that from Kangaroo Valley (NSW South Coast) being associated with and caused by volcanic intrusions. It is quite different to some I collected from the Moon Plains in SA and Deep leads of the Nundle area, neither of which contain chalcedony but resemble Silcrete. To my understanding Silcrete and opal do precipitate at low temperatures up to 140c but chalcedony, jasper/agate form from 140c to 300c bit above normal ground temperatures. The ph of the solution is also a factor. In fact in specimens from Kangaroo Valley the initial petrification was by jasper/chalcedony often preserving the original wood grain and later cracks were infilled by common opal bearing no relationship to the original wood grain, different precipitation temperatures. Also in Kangaroo Valley the petrified wood becomes blacker closer to the volcanic plug becoming more petrified charcoal in the immediate vicinity.
As to theory fitting the facts I recall the story of a geo student given a mapping project in SA, 10 sq km of horizontally bedded Sandstone with occasional silcrete, after a fortnight map was done but he walked up the highest hill to take in a last view, avoided because of the heat and flies until then and found sitting there on the silcrete a 40 ton boulder of granite. How did he explain that Its not there. He He and now he is a geo professor in Vic.
Ref THE AMERICAN MINERALOGIST, VOL.46,JANUARY_FEBRUARY, 1961 SYNTHESIS AND ORIGIN OF CHALCEDONY*
I have to agree with Lefty regarding the chalcedinized petrified wood he finds in Queensland, and that from Kangaroo Valley (NSW South Coast) being associated with and caused by volcanic intrusions. It is quite different to some I collected from the Moon Plains in SA and Deep leads of the Nundle area, neither of which contain chalcedony but resemble Silcrete. To my understanding Silcrete and opal do precipitate at low temperatures up to 140c but chalcedony, jasper/agate form from 140c to 300c bit above normal ground temperatures. The ph of the solution is also a factor. In fact in specimens from Kangaroo Valley the initial petrification was by jasper/chalcedony often preserving the original wood grain and later cracks were infilled by common opal bearing no relationship to the original wood grain, different precipitation temperatures. Also in Kangaroo Valley the petrified wood becomes blacker closer to the volcanic plug becoming more petrified charcoal in the immediate vicinity.
As to theory fitting the facts I recall the story of a geo student given a mapping project in SA, 10 sq km of horizontally bedded Sandstone with occasional silcrete, after a fortnight map was done but he walked up the highest hill to take in a last view, avoided because of the heat and flies until then and found sitting there on the silcrete a 40 ton boulder of granite. How did he explain that Its not there. He He and now he is a geo professor in Vic.
Ref THE AMERICAN MINERALOGIST, VOL.46,JANUARY_FEBRUARY, 1961 SYNTHESIS AND ORIGIN OF CHALCEDONY*
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Lol!
Yes, there can sometimes be a difference between what is supposed to be somewhere versus what actually is there.
The more years I spend chasing rocks about the bush, the more I appreciate the simple wisdom of old sapphire miners living in tin shacks in the bush, who will always tell you that at the end of the day - the stones are where you find them. This has to be one of the truest statements out there.
Shows you just how incredibly complex our earth really is.
That said, geology is a solid science and it's nearly always right - it's just that reality decrees that there are exceptions to pretty much every rule. And of course, many now discredited ideas were once held up as unimpeachable scientific fact in their day, until somebody proved otherwise.
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Ted, is the Kangaroo valley pet wood often glossy?
Much of the Fitzroy river stuff has a very high gloss on the surface, despite having been tumbled along a river. Some bits of material also have a slightly "melted" or glazed surface appearance.
The extinct volcanoes cores around the river, the presence of chalcedony on and sometimes in the wood and the often glazed appearance all suggest to me that volcanics were an important factor in the petrification process of this stuff. But not having a scientific background I can really only put things together based on what I see in front of me.
Much of the Fitzroy river stuff has a very high gloss on the surface, despite having been tumbled along a river. Some bits of material also have a slightly "melted" or glazed surface appearance.
The extinct volcanoes cores around the river, the presence of chalcedony on and sometimes in the wood and the often glazed appearance all suggest to me that volcanics were an important factor in the petrification process of this stuff. But not having a scientific background I can really only put things together based on what I see in front of me.
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Lefty, Some of the petrified wood from Kangaroo Valley that replaced by chalcedony or jasper is glossy on the outside, some shows obvious burning on the margins which has been fossilised as well.Much of it is dull grey on the outside tumbled in a river. Yes Geology is a solid Science but the net is not and sweeping generalisations based on info from US websites perhaps valid with regard to Arizona should not be taken as gospel for conditions here.Yes my geo qualifications are pre-internet.
Interestingly I have found baked cobblestones in deepleads where lava has flowed down ancient river valleys and turned them to citrine high temperatures indeed. Good that you moved Springsure back to central Queensland because I like a bit warmer when I travel through, than the New England in June. Ted
Interestingly I have found baked cobblestones in deepleads where lava has flowed down ancient river valleys and turned them to citrine high temperatures indeed. Good that you moved Springsure back to central Queensland because I like a bit warmer when I travel through, than the New England in June.
Ted
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A couple of petrified wood look alikes.
The above turned out to be a haematite lump from Grabben Gullen there is a magnetite iron ore deposit in the area.
The second a silicified rhyolite from Pambula South Coast NSW
The above turned out to be a haematite lump from Grabben Gullen there is a magnetite iron ore deposit in the area.
The second a silicified rhyolite from Pambula South Coast NSW
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That rhyolite looks like it would make good cabbing material - not sure about hardness/integrity but I like the patterns.
You won't want to be in Springsure, central QLD right now.....it will be getting warm to the point of brutal I want to get back there and grab some more labradorite - a small number of the pieces contain metallic-looking inclusions that resemble bright, newly smelted copper and a small number of others show white or blue adularesence and I have had a geologist and a gemmologist enquire about getting some for study. Most of it is just a transparent straw colour (which facets a surprisingly attractive and bright stone despite the lower RI).
The number of pieces of petrified wood that I have found in areas without any obvious volcanics close by, I can count on one hand - not suggesting that this is the case elsewhere. The few that I have found like that seem to have a bit of a different quality to them - definitely fossil wood but duller in appearance without the gloss.
You won't want to be in Springsure, central QLD right now.....it will be getting warm to the point of brutal
I want to get back there and grab some more labradorite - a small number of the pieces contain metallic-looking inclusions that resemble bright, newly smelted copper and a small number of others show white or blue adularesence and I have had a geologist and a gemmologist enquire about getting some for study. Most of it is just a transparent straw colour (which facets a surprisingly attractive and bright stone despite the lower RI).The number of pieces of petrified wood that I have found in areas without any obvious volcanics close by, I can count on one hand - not suggesting that this is the case elsewhere. The few that I have found like that seem to have a bit of a different quality to them - definitely fossil wood but duller in appearance without the gloss.
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From the geological data provided in comment number 26 in this thread...
These areas are relatively close together and the interesting thing is the difference in interesting things produced by these related (is that right or wrong?) volcanic events.
Clermont is a gold mining district a little to the north of Emerald - I have not heard of any gemstones coming from there (happy to be corrected).
Emerald is a short distance from the Anakie field, one of the worlds major sapphire producing areas. Zircons and pleonaste are also abundant.
Springsure in CQ is a short distance south of Emerald - labradorite and opalized wood are found there.
Gold is found at the Anakie field but nothing like the quantities at Clermont. Sapphires, zircons and spinel are seemingly absent from Springsure, as labrodorite and opalized wood are from the Anakie field.
Pretty interesting.
These areas are relatively close together and the interesting thing is the difference in interesting things produced by these related (is that right or wrong?) volcanic events.
Clermont is a gold mining district a little to the north of Emerald - I have not heard of any gemstones coming from there (happy to be corrected).
Emerald is a short distance from the Anakie field, one of the worlds major sapphire producing areas. Zircons and pleonaste are also abundant.
Springsure in CQ is a short distance south of Emerald - labradorite and opalized wood are found there.
Gold is found at the Anakie field but nothing like the quantities at Clermont. Sapphires, zircons and spinel are seemingly absent from Springsure, as labrodorite and opalized wood are from the Anakie field.
Pretty interesting.
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These volcanic events may be thought of as elevators and whatever the lava comes through may determine what minerals they bring up. Chudley Park, Moonstone Hill are similar peridot bombs, feldspar bombs, spinel, sapphires and zircons. The heated silica rich waters may deposit quartz veins with copper minerals or gold or silicify to produce jaspers, chalcedony etc. Depends what they come up through and two eruptions only km apart may have come through quite different rocks. Grabben Gullen near Crookwell produces blue, green and yellow sapphires but 30 km south at Tumbarumba the lavas have intersected chrome rich serpentinite resulting in pink and red rubies.
The silicified rhyolite pictured is great cabbing material and has been carved overseas. There are ancient( Devonian) rhyolites, iron rich thus the red colour and usually quite porous, on the NSW far south coast and near Pambula they have been silicified to resemble a banded jasper.
The silicified rhyolite pictured is great cabbing material and has been carved overseas. There are ancient( Devonian) rhyolites, iron rich thus the red colour and usually quite porous, on the NSW far south coast and near Pambula they have been silicified to resemble a banded jasper.
Wow this is fantastic stuff, thanks guys.
I started my geology degree after doing a short weekend course on the geology of gold, i was hooked straight away. Doing the course part time though, so after three years part time i have only completed the first years units. Have a long way to go and a lot to learn, but i do enjoy a good discussion about geology, rocks and minerals.
fossickeract would that silicified rhyolite be what i have heard others refer to a ribbon jasper or is there a separate deposit?
Also wondering if you get to Kangaroo Valley much? Would love to have a talk about the geology of the area if you don't mind someone picking your brain a bit.
I started my geology degree after doing a short weekend course on the geology of gold, i was hooked straight away. Doing the course part time though, so after three years part time i have only completed the first years units. Have a long way to go and a lot to learn, but i do enjoy a good discussion about geology, rocks and minerals.
fossickeract would that silicified rhyolite be what i have heard others refer to a ribbon jasper or is there a separate deposit?
Also wondering if you get to Kangaroo Valley much? Would love to have a talk about the geology of the area if you don't mind someone picking your brain a bit.
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fossickeract said:
That gives a lot of weight to observations miners have made on the Anakie field - different-coloured stones will often predominate in different areas of the field. When we had our claims at Russian gully many years ago, all colours were present but blue was heavily predominant. At the other spot some 15-20km away up the other end of the field, green seems to predominate. I've heard of small spots where yellow predominates - there are approximately 70 extinct volcano cores on the field.
It seems that when it comes to what volcanoes leave behind, locality matters - even over very short distances!!!
