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Author Topic: a simple test for gold in pryrite  (Read 38754 times)

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Offline bama

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a simple test for gold in pryrite
« on: July 06, 2009, 09:58:45 AM »
Hey folks,
In a nugget patch I've been working there is vein of green stone(chorite shist). It really sounds off my metal detector. I think it is loaded with pryrite. Is there a simple test for gold I can do? Also around this vein is decomposed bedrock that has a lot of black sand, not much gold. Could this sand contain gold that isn't
visible to the eye? Any suggestions that don't involve costly assays?

bama

Offline krueger95

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Re: a simple test for gold in pryrite
« Reply #1 on: July 10, 2009, 11:01:40 AM »
Hello-
I'm new here-- so please forgive me for sticking my nose in here.
I too am very interested in a simple test for gold or silver in pyrites. We have chalcopyrite and some rusty red material in quartz and then some silphides. Was told that they recovered gold and silver from this ore 60 years ago but no one is available to tell me more.
So---- I'm looking for a simple "bench top" test for gold and silver.
Thanks.
Stan

ClickTheYellowChick

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Re: a simple test for gold in pryrite
« Reply #2 on: July 10, 2009, 12:45:23 PM »
Welcome aboard, Montana Krueger!  <-wave->

Great first question!  If there is something "bench top simple" out there, I'm sure this group's members will know about it.

I personally have seen pyrites and gold on the surface of the same rock.  Wish I had one in my specimen collection, but alas, it belonged to someone else.

Again, Welcome!  ;D

Kind regards


Offline GollyMrScience

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Re: a simple test for gold in pryrite
« Reply #3 on: July 10, 2009, 06:29:15 PM »
I have pics of gold in pyrite through a microscope that only starts to show gold within the striations of the pyrite at 150 power. Some does not show up till you get to electron microscope so that stuff can get REAL tiny.
There are some basic tests that can be done but they are generally pretty course and will only give you results if larger amounts of gold.
Are you looking for a field test to just confirm that gold is there?
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline krueger95

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Re: a simple test for gold in pryrite
« Reply #4 on: July 10, 2009, 07:06:24 PM »
It would be very nice to find a field test for gold &/or silver in pyrites and sulfides.
Any suggestions ?
Thanks for your assistance.
Stan

Offline gpg

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Re: a simple test for gold in pryrite
« Reply #5 on: July 19, 2009, 08:40:13 AM »
THis was posted by Geowizard on the Alaska Gold Forum.

For iron pyrite (sulfide), here's the test:

(In a ventilated area... using a small sample)

Crush and roast the sample at high heat.

When iron sulfide is roasted, the sulfur vaporizes and results in iron.

The iron will pick up with a magnet.

Offline PlacerPal

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Re: a simple test for gold in pryrite
« Reply #6 on: July 19, 2009, 12:40:18 PM »
Interesting information from Bob Redberg about gold and iron pyrite.

"The reason most prospectors know a lot about the appearance and habits of iron pyrite is twofold:
1) To keep from being fooled.
2) Because of the known association between pyrite and gold. Pyrite is found in, or asociated with,
more than 70% of the world's gold deposits."

Topics:

The Mysterious Process That Traps Gold in Pyrite

Nature's Method of Releasing Gold from Pyrite

The Commercial Process for Recovering Gold From Pyrite

And much, more more.

Interesting Things About Gold

 :)

Offline GollyMrScience

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Re: a simple test for gold in pryrite
« Reply #7 on: July 19, 2009, 05:41:23 PM »
Well I would probably want to add some details to some of what is written.
The Carlin Gold IS visible and ranges in size from flour to microscopic. Under an electron microscope the gold can be seen as blebs in the pyrite and even as coatings in the striations of crystal sulphides. This is common with many sulphide sourced gold.
He states that gold is found in the form of iron pyrite but gold is found in the form of gold and pyrite as pyrite its just that they are sometimes in very close association.
One confusing aspect is that gold found in host rock containing sulphides can have free gold, gold in association with sulphides, and gold right in the sulphides. For a panner finding gold from that kind of ore they are panning the "nuggets" and will never see the ultra fines.
It would be unfair to characterize the iron pyrite as the host when in fact many of the sulphides can be found in association. Often as a mixed bag of sulphides as during formation the sulfur was complexing with different metals. Arsenic, Iron, Copper etc and any and all of them could be associated with gold.
The idea of roasting has merit and has worked to some degree in the past though it was not so good until chloriation and cyanide came into wider use. Some mills did roast to break down the sulphides before stamp milling and mercury plates and the process did increase gold recovery but the mercury systems just could not get at a lot of the gold and even after roasting the ores were often a pain as they caused contamination of the mercury and both gold and mercury losses.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline Gotrek

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Re: a simple test for gold in pryrite
« Reply #8 on: July 21, 2009, 11:46:06 AM »
As a simple rough field test you could carry some Stannous Chloride with you, place a drop on the rock let it wok for a bit and transfer the drop to a dry tissue.  The color purple in stain would indicate the presence of gold.

You can make a Stannous Chloride solution by adding Tin to hydrochloric (muriatic) acid and dissolving it over heat.

the solution can easily be carried in a small vial along with a droper, tissue and "Q-Tips"  Store it in a dry dark container and it should last for a few days.  But it does not keep for extended periods.  The good new is you can renew it by adding more tin to the mix.Delos Toole Free Articles

EDIT: sorry I'm not clear enough in my post.  You would first have to place a drop of Aqua regia or acid/peroxide on the sands/stone to sample to dissolve the gold (if present) then test with the stannous chloride solution.  Sorry about that.  Let me know if it's still unclear. 

May not be the most efficient way but quick and easy to carry.

ClickTheYellowChick

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Re: a simple test for gold in pryrite
« Reply #9 on: July 21, 2009, 12:09:29 PM »
As a simple rough field test you could carry some Stannous Chloride with you, place a drop on the rock let it wok for a bit and transfer the drop to a dry tissue.  The color purple in stain would indicate the presence of gold.

You can make a Stannous Chloride solution by adding Tin to hydrochloric (muriatic) acid and dissolving it over heat.

the solution can easily be carried in a small vial along with a droper, tissue and "Q-Tips"  Store it in a dry dark container and it should last for a few days.  But it does not keep for extended periods.  The good new is you can renew it by adding more tin to the mix.
Delos Toole Free Articles

Hi, GoTrek,

That Delos Toole set of articles is a neat set of resources you shared in your link.  Good Job! <-yes_>

Suggesting a stannous chloride field test for presence of gold in a sample, will NOT meet with the desired outcome, especially on a pyrite, the topic of this thread.  May I elaborate?

You are correct in your edit: Gold has to already be in dissolved, aka be in ionic form, within an acidic solution, before the Stannous Chloride protocol will work as you described.  

And if it is a sulfide you are working at trying to digest in order to test, such as pyrite is, even attempting to digest the gold trapped in the sulfide in the first place with A/R is going to present a hindering challenge before even trying to use the Stannous Chloride test.  Trying to digest gold in the presence of a sulfide is something like a Catch 22 experience.  Any gold digestion will quickly be involved in a circular-type reaction, rendering it difficult for stannous chloride to achieve a "positive identification" chemically using acid dissolved tin.

While always being prepared with a portable kit containing gold testing acids, I'm not sure I'd carry such a field kit of acids, but that's just me.

Kind regards,
Megan

 


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