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Author Topic: How to test rocks to see if gold looking stuff is really gold?  (Read 99554 times)

Offline Bored chemist

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Dynamite may prove easier to get than a mining license.
 

Offline Bass

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Just got back from the little jewellery repairer, who tested the rock using acid, confirmed there is definitely a percentage of gold in the rocks, except it is of such low volume it would require a huge process in order to extract sufficient quantities. Apparently if it was not gold it should have turned green with high strength acid, observed to be giving off serious vapour even before it made contact with the rock. Anyone know where I can get my hands on some dynamite?

Andrew- likely there are very low concentrations of gold in your rock.  Google "sed hosted gold deposits" and you'll find that there are plenty of carbon-rich shale gold deposits, typically very low grade but very large.  If you are really interested in how much gold is in these rocks, take them to an assayer (fire assay is the most accurate).  For around $20-$30 (in the US) they will give you the concentrations in parts per billion.  Commonly these deposits host gold as auriferous pyrite, that is pyrite crystals with minute inclusions of gold either in the crystal or surrounding the crystal.  In the trade, we call this "no-see-um" gold, because it is not visible, even under a microscope.  Some of the mines in Nevada are now profitably mining grades of less than 0.03 ounces of gold per ton of rock (approx 1 ppm).  So if you have at least 1 ppm gold in your samples, and you don't mind a bit of cyanide, and you have at least $100,000,000 that you are willing to invest as capital for the mine and processing- I say go for it!  Better yet, purchase the property (and the mineral rights) then sell for an obscene profit to a mining company.
 

Offline JimBob

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OK, Bass just got there ahead of me. SO - my composition.

He used Aqua Regis - Hydrochloric and Nitric acid - serious stuff.

Why didn't you say Devon in the first place. Yes, gold is possible in Devonshire. Most of the Roman gold mines were in Wales. Don't know about Devon but it is VERY possible with the other mineralization in the area.

Since this is an oil shale you found the gold in, it is gold that has been eroded from its source a redeposited in another place - probably a fern swamp or bog. So finding the source would be a better deal. Placer deposits such as this are not common.

Do some research first - I just did a quick search and this is what I came up with this:

Epithermal gold mineralisation - Devonian rocks N. Britain. Publication
http://www.ukge.co.uk/UK/prodtypebook.asp?PT_ID=165

Also research placer gold deposits.

Good luck!
 
« Last Edit: 08/11/2007 23:03:32 by JimBob »
 

Offline Andrew K Fletcher

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Bass, Jim, thanks for the links and direction to research this. From my own prospective, just happy that I am still alert enough to spot a few things that others have missed :) Including my first few specs of gold :) Not really considering spending a few thousand K on some rocks that have some gold present and even if I did, this country would soon be on my back if I began blowing up the National Trust's land :) For now I am content that my instincts about this slate and it's content have been justified.
 

Offline Bass

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Since this is an oil shale you found the gold in, it is gold that has been eroded from its source a redeposited in another place - probably a fern swamp or bog. So finding the source would be a better deal. Placer deposits such as this are not common.

Do some research first - I just did a quick search and this is what I came up with this:

Epithermal gold mineralisation - Devonian rocks N. Britain. Publication
http://www.ukge.co.uk/UK/prodtypebook.asp?PT_ID=165

Also research placer gold deposits.

JimBob, if there is low-grade gold present in these rocks, it would be epithermal (shallow hot water created deposits), not placer.  Shales are too low energy to host placer gold.  Paleo placers (placer deposits in old rocks) are almost always found in conglomeratic rocks, and/or mixed conglomerate-sandstones (beach placers)- the Witwatersand is a prime example.  Current thinking for shale hosted gold deposits is that the carbonaceous material acts as a reductant for passing hydrothermal fluids- making it an ideal host for metallic sulfides and/or epithermal gold.  Most of the Nevada sed-hosted gold deposits also contain hydrocarbons.
Andrew- again, the metallic minerals that you see in those specimens is almost certainly pyrite, possibly marcasite, pyrrhotite, or arsenopyrite.  I very much doubt there is any visible gold- any contained gold would be in the form of minute inclusions that are too small to see.  The only real test for the presence of gold is an assay.
« Last Edit: 09/11/2007 17:25:58 by Bass »
 

Offline JimBob

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OK, Thanks Bass. Learn something new every day.

(Darned hard rock stuff, never got it down when in school and still in almost complete ignorance of it. At least I sold my prospect and joint venture idea - we'll be taking a bath in oil soon when the wells are drilled!)
 

Offline Andrew K Fletcher

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http://www.museumwales.ac.uk/en/838/

http://www.museumwales.ac.uk/en/838/

Did research placer deposits, pictures from Wales show similar rock structure to where I found the rocks. Also in close proximity there is red sand stone, quartz and calcite and evidence of a huge land shift and tectonic plate movement, though the location for the slate is predominantly dark grey and soft crumbly graphite in structure with very few pockets containing the speckled deposits. There are no fossils in this area either.
 

Offline JimBob

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Perhaps I should reconsider my total capitulation to Bass? What do you think, Andrew?

Were the fractures associated with the pockets of speckled deposits?
 

Offline Andrew K Fletcher

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Yes they were Jim, the whole area has been turned on its side with the rock formation tilted to an acute angle.

I am not an expert in geology as you guys are. But one other point is that the area I found this in has the coloured slate deposits on the higher ground above the rock formations and there is a great deal of land slip. Some of the speckled deposits can be seen a setteling in a swirling plughole motion, frozen in the rock almost as if stopped in motion. Some of the speckles are more copper coloured and larger than others, but they don't look like copper and there is no oxidisation whatsoever.

I can send you a sample if you want.

Andrew

Perhaps I should reconsider my total capitulation to Bass? What do you think, Andrew?

Were the fractures associated with the pockets of speckled deposits?

 

Offline JimBob

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Then epithermal gold is more likely than placer -  I think. The red sandstone is probably the Old Red, a Devonian sandstone so this area you are investigating has a good chance of being one of the areas described in the book reference I found.

Send me a Rock? See PM
 

paul.fr

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let me tell you a story...........

oops, i now realise this topic is about gold and ore's
 

Offline Karen W.

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No fair where did you tell the story I want to hear! LOL
 

Offline Andrew K Fletcher

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Went back today with my new scintillating pager to see if the rocks on this beach are radioactive and found they were registering around 15 18 counts per second with a couple of peaks at 25 CPS when the counter was held close to the rock face, although even the land slips in this area read around 15-16 cps when other areas of coast are down around 3-4 CPS Fascinating.

Can someone identify these impregnations in what appears to be oilslate with a soft crmbly graphite texture.











 

Offline Bass

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How to test rocks to see if gold looking stuff is really gold?
« Reply #38 on: 14/03/2008 01:00:27 »
Andrew
Carbon makes a marvelous reductant.  Uranium (thorium to a lesser extent) is easily oxidized and taken into solution by surface waters- and just as easily precipitates in the presence of a reductant.  Higher than background radioactivity is common in graphitic shales from around the world.  Of the several types of Uranium deposits, two that account for much of the world's supply form this way:  unconformity-type deposits and roll-front deposits.  Both form by precipitating oxidized uranium carried in groundwater and concentrating it either  at the redox boundary or in local reducing conditions.
 

Offline Andrew K Fletcher

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How to test rocks to see if gold looking stuff is really gold?
« Reply #39 on: 15/03/2008 20:55:30 »
Thanks Bass, this explans why the hotspots were found near cracks where the rock formations are at different angles to each other. There is iron / rust deposits here and a strange darker red colour that gives off the most counts per second. This is from obvious leeching of water so confirms your expert opinion.

P.S. Having fun with new Gammarae Pager, scintillating detector. Will be putting some videos of a Former soviet Nightsight that my friend brought round because he thought it might contain some radioactive material. Boy was he correct. Interesting thing is that the only power source is what looks like a very old green 9v battery. When the switch is flipped a shield, (presumably) is moved and allows gamma rays to be released. Fascinating bit of kit, great for scanning the local surroundings in the dark. Sorry for waffling on on this thread.
 

Offline Bored chemist

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How to test rocks to see if gold looking stuff is really gold?
« Reply #40 on: 16/03/2008 19:00:15 »
Isn't Xray production from the EHT of an image intensifire a more likely cause of the signal on a gamma counter?
Why would a nightsight have a radioactive source in it?
 

Offline Andrew K Fletcher

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How to test rocks to see if gold looking stuff is really gold?
« Reply #41 on: 16/03/2008 22:07:03 »
Thats a good possibility also, but can't see a 9v battery supplying suficient xray output, maybe i am wrong, I simply don't know enough about this nightsight, it looks world war 2 ish but have not found one that looks like it and been searching quite a lot to identify it.

BTW the radiation comes from inside a steel covered container, not through the lens.

 

Offline Bored chemist

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How to test rocks to see if gold looking stuff is really gold?
« Reply #42 on: 17/03/2008 20:23:53 »
Just to get back a bit nearer the topic, if that stuff is significantly radioactive rock you can probably sell it on ebay for more than the gold is worth.

(9 volts and an inverter circuit can certainly generate xrays but the flux should be tiny. Bad interference supression is another idea to explore but preferably not in this thread)
 

Offline scottish gold

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How to test rocks to see if gold looking stuff is really gold?
« Reply #43 on: 18/03/2008 13:42:23 »
Hi Andrew,

Might be worth buying a gold pan and trying the sediments of any streams that are nearby for a show of gold? If there's traces of gold in your samples, maybe get a flash in the pan :-)

You never know!



 

Offline Bass

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How to test rocks to see if gold looking stuff is really gold?
« Reply #44 on: 18/03/2008 14:36:56 »
Hi scottishgold

Welcome to the forum!  Another rocker, YES!

Panning is a great idea- sulfides will break down and any contained gold should be liberated.  There are a few gold districts where the gold is so fine, it doesn't show up when panned (some of the Nevada sed-hosted deposits).  But this is the way almost all gold deposits were found in the days of iron men and wooden ships.
 

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How to test rocks to see if gold looking stuff is really gold?
« Reply #45 on: 18/03/2008 20:00:56 »
I just suggest you don't ask the Ethiopian central bank to do an assay for you.
 

Offline Andrew K Fletcher

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How to test rocks to see if gold looking stuff is really gold?
« Reply #46 on: 23/03/2008 20:21:13 »
How about on a beach which is pretty sheltered in a cove, having dark graphite and sand with quartz and oilslate rock formations locally. How does this pan out so to speak?
 

Offline Bass

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How to test rocks to see if gold looking stuff is really gold?
« Reply #47 on: 23/03/2008 23:56:17 »
Andrew, give it a try.  I wouldn't expect you to find anything, but panning takes little time and effort.  Try to either collect sand that is on bedrock, or find places in the sand where heavy minerals (magnetite, limonite, hematite, illmenite, zircon) collect (a magnet wrapped in Saran Wrap will help you find magnetite if any exists). 
Don't know if you've tried panning before, but best to fill the pan about 3/4 full, then in calm water, work the sand/gravel with your hands until you get rid of all the mud/silt (fill the pan with water, work the sediment until muddy, then pour off the muddy water- continue until water stays somewhat clear when stirred up).  The green platic gold pans with riffles built in make this much easier.
Fill with water, then rock the pan gently back and forth while slowly swirling it in a circular motion (this is to get the heavy material to sink to the bottom).  After you've agitated the pan enough to get the heavies to sink, slightly tilt the pan and allow the water with the top layer of light material to wash out.  You can dip the tilted pan into the water several times to allow the top material to wash out.  Fill with water again, swirl and rock the pan, flush out the top layer.  Repeat this until only a small amount of material remains in the bottom of the pan (often this will be mostly black).  You can pick out any obvious non-mineralized pieces of gravel, as these will also sink to the bottom since they are heavier than the sand.  Gently swirl the pan letting the heavy material in the bottom move a few mm at a time, then use a magnifying glass and see if a thin gold line exists at the back (the gold will not move much since it is heavier).
With practice, you can do this in a few minutes- first timers generally take 15-25 minutes.  This is much more enjoyable when the air and water temperatures are warm, otherwise wearing waterproof gloves really helps.
Good luck and have fun!
 

Offline Andrew K Fletcher

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How to test rocks to see if gold looking stuff is really gold?
« Reply #48 on: 27/03/2008 19:13:23 »
Cheers for that Bass, gonna give it a go, cant think of a nicer place to be than on a beach in Devon in glorious sunshine a lovely wife and 4 bull terriers to protect my claim lol. Shall I take a few beers with me? Hmmmmm lemme think about this. Magnets a good idea also.
 

Offline yor_on

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How to test rocks to see if gold looking stuff is really gold?
« Reply #49 on: 03/03/2010 09:15:54 »
And remember, if you ever need some help, ah :)

Really cool read.
 

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How to test rocks to see if gold looking stuff is really gold?
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