Another question..
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Reefs would be formed from metal and mineral bearing hot pressurised fluids depositing their loads under favourable temperature, pressure, chemical and circulatory conditions along the original crack that allowed the penetration of such fluids from an underlying magmatic zone.
Over time these reefs can be expanded by seismic events and successive intrusive pulses of the fluids. The quartz can often be seen be seen to be "laminated" by bands of slate as a result of these successive intrusions.
The host rocks here in Victoria are often highly carbon bearing slates formed from the muds of an ancient sea. Leaching of the silica content of these rocks by the fluids could leave behind a band of highly carbonaceous rock perhaps further enriched with minerals such as iron oxides and sulphides as the fluids percolate the host rock.
It is thought that many of the visually recognisable "indicators" in Victorian goldfields formed in this manner.
Another consequence of this process is that if the gold bearing fluids are able to penetrate the host rock for long periods, the host slate rocks themselves can become gold bearing to some extent away from the actual reef line. The gold contained in these "gold slates" was not known to be nuggety but in some places was quite high and is known to have been crushed for its fine gold content.
You may be on to something and perhaps If you are able to provide a photo of the black seam, it would be enlightening.
Over time these reefs can be expanded by seismic events and successive intrusive pulses of the fluids. The quartz can often be seen be seen to be "laminated" by bands of slate as a result of these successive intrusions.
The host rocks here in Victoria are often highly carbon bearing slates formed from the muds of an ancient sea. Leaching of the silica content of these rocks by the fluids could leave behind a band of highly carbonaceous rock perhaps further enriched with minerals such as iron oxides and sulphides as the fluids percolate the host rock.
It is thought that many of the visually recognisable "indicators" in Victorian goldfields formed in this manner.
Another consequence of this process is that if the gold bearing fluids are able to penetrate the host rock for long periods, the host slate rocks themselves can become gold bearing to some extent away from the actual reef line. The gold contained in these "gold slates" was not known to be nuggety but in some places was quite high and is known to have been crushed for its fine gold content.
You may be on to something and perhaps If you are able to provide a photo of the black seam, it would be enlightening.
A bloke I'm working with ATM use to drill and blast in the Ballarat mine. I said "was the gold in a black material each side of the viens?" he said yeah but it was this grey to black material that had a chocolate fudge texture to it, that's what the gold was in (all nugget gold).
This isn't the material I'm talking about but still interesting.
Where is Goldierocks when we need him?
Buggered if i'd go that far down, it was hard enough going into the Long Tunnel mine in Walhalla.
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Jaros back in 1963 myself, brother, my best mate, and now wife entered the long tunnel and did some exploring. My brother and the wife went back out when we crawled over an area that had collapsed and had a very narrow access. My mate and I went a bit further on, and climb up a Shaft that had a long vertical log in it. These days you have to go in via a guided tour but it was fully open a bit past the machine cavern then.
I'm going back to the late sixties -still the wild East.
Have attached some info on indicators. Indicators were thin fluid channels that ran parallel with the rock strata. Being differently coloured because of mineralization they were easily recognised within the rock strata. Where they intersected reefs the gold was often found to be nuggety a fact not wasted on the old timers.
In Ballarat and other places once concentrations of gold in a reef were found to be associated with these thin but recognisable seams within the rock, miners often abandoned sinking or driving on the quartz and mined along the indicator seeking places where other quartz reefs were intersected and rich patches could be expected.
However if these two intersected at low angles, or with reefs faulted along the indicator plane, that could be consistent with what 20x described as his mates experience.
Ballarat Gold would have been working on the same line as “the indicator” which stretched from Black Hill in the north to Sovereign Hill in the south.
In Ballarat and other places once concentrations of gold in a reef were found to be associated with these thin but recognisable seams within the rock, miners often abandoned sinking or driving on the quartz and mined along the indicator seeking places where other quartz reefs were intersected and rich patches could be expected.
However if these two intersected at low angles, or with reefs faulted along the indicator plane, that could be consistent with what 20x described as his mates experience.
Ballarat Gold would have been working on the same line as “the indicator” which stretched from Black Hill in the north to Sovereign Hill in the south.
What's the book, Geoff?
Yes its the Prospectors guide to Victoria. I bought mine in the early 60s just out of school. Page 117 is from the edition I have so maybe there is a difference between Axtyrs edition and mine.
These are the notes from the National Library of Australia about the publication.
These are the notes from the National Library of Australia about the publication.
- First published as "Miner's handbook" 1894-1897. Reprinted as "A guide for prospectors in Victoria" 1931- 32. Reprinted and revised as " Prospector's guide" 1936 - 10th ed. 1980. Reprinted and revised 11th ed. 2004.
I’ll have a better look at the one I saw in Lucky Strike next time I’m there ogling some gear. Will let you know if there are any major differences.
