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a simple test for gold in pryrite

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GollyMrScience:
As Chick suggests you will need to get that gold into solution.
Hard to get out of doing a complete work up of grinding the sample to liberate gold,adding acid chemistry (aqua regia), filtering and then testing the solution.
It sounds way harder than it is and once you are set up for it its no big deal. The sulphides need to be handled too which is why roasting is often done first.
I have seen a couple of kits available for testing with pre made chemistry but its not that hard to make up your own.
The stannous chloride will tell you that there is gold but other than the reaction intensity there is really no way to easly get a quantitative assay.
At one point in my life I was carting around a bush assay lab capable of doing basic assays with a torch and a microscope to check bead size. I even went so far as to put together a small single dish scorifying oven. Down and dirty assays in the evenings in camp. Lots of work and eventually I just quit all the hassles and took lots of samples and either took them back to my own lab or sent them off for commercial assay.
Sample anything that does not jump up and run away. Take careful notes and take it back someplace comfy like to work on. In the bush its better to cover the ground and take the samples and not slow down for nuthin'!

ClickTheYellowChick:
Golly,

I LOVE your closing summary line o'thought...."sample anything that doesn't jump up and run away."  

EXCELLENT way to put it!   <-yes_>

That goes for pyrites, non-pyrites, quartz, granite, basalt, and about a bazillion other occurrences!

Megan

PlacerPal:
Hi Gotrek,

Well, here we go again. The Mavericks are playing in the background. ;D

A Stannous Chloride (SnCl2) field test for presence of gold in a sample, CERTAINLY could meet with the desired outcome!

Prospectors, Geologists, GeoChemists, Chemists, Lab Techs, etc. have used the test for..... well what seems like forever for me. 

One can buy a gold test kit today that can do the test very well and it is not affected by "sulphides". I know because I have
the chemicals on the shelf in my lab within 6 ft of me, I use them and I have beakers containing the test solutions waiting
for precipitation of the gold. I used the stannous chloride to test the solutions for gold which is already evident by the yellow
colour and I use the stannous chloride to test the solutions after gold precipitation to check and make sure all the gold has
been precipitated.

I could put a relatively non-toxic gold test kit together in about 5 minutes. But then I would have to write the Operators
Manual suitable to cover all types of test samples. That would take time stolen from my present effort writing instrument
installation, operating and maintenance manuals - instruments we manufacture to do chemical analysis. Maybe I will do it
when I get a "round tuit"  ;)

Getting back to the Delos Toole article and method for gold testing, the method probably worked just fine for Toole and may
others who were testing possible gold ore samples. Toole referred to testing ore concentrates, which "used to mean" to anyone
familiar with the mining industry, to be the crushed and milled ore samples ready for the leaching plant or the smelter, not
the chunky bits of rock with waste. Toole should have been more clear and specified a crushed, milled and well mixed ore sample -
the concentrate.

Toole did not carry Aqua Regia into the field which is good. He mixed small amounts hydrochloric and nitric acids to make
Aqua Regia (AR) along with the ore sample in a test tube out in the field. Then he boiled the acid/ore mixture for 5 - 8 minutes
over a lamp flame which would have driven off any sulphides as SO2 and any other gases such as the toxic NO and NO2 leaving
the leached auric gold chloride AuHCl3 in solution. Now Toole has the gold in solution and he has driven off the sulphides. We are
 ready to test the leachate for gold.

The tin chloride (stannous chloride - SnCl2) test is an excellent test for gold. Just blot some of the leachate solution onto an
absorbent material like a filter paper, a tissue, some toweling or better the thick absorbent paper fibre paint clean-up "rag" that
comes in a roll. Then add a drop of the tin chloride to the blotted area. A light pink colour - minor gold, darker pink - more gold,
heavy pink/purple colour - major gold.

The Delos Toole gold test method probably was never intended to be used to test iron pyrites which was known as Fools Gold
and usually quickly discarded. The method was intended to be used to test gold-platinum-palladium ore samples. However the
method could be revised to test pyrites for gold. The pyrites crystal samples would have to crushed and milled to a fine powder.
The powdered sample roasted to drive off the sulphides reducing the sample to iron, gold and any other precious metals if present
and then leached and tested. Caution roasting as the pyrite may contain arsenic and the arsenic sulphide fumes are major toxic g
ases at very low ppm!

Tin Chloride is dead simple to make by anyone. The Source in Canada, called Radio Shack in the USA, as well as other electronics
suppliers sell a tin solder that is 99% tin. Simply dissolve a length of the tin solder in HCl (Muriatic Acid), put the solution in a
brown glass bottle with an eye-dropper combination cap. Add a few inches of the tin solder to the solution to compensate for
deterioration and then off to the field to do gold testing with the tin chloride! Oh yes, take along the sample crusher, the leachate,
the glass test tubes, blotting paper and a mini butane torch for a heat source. If testing iron pyrite, take along a roaster too - a
stainless steel tablespoon with a wood handle to hold the pyrite/gold sample in the flame until the sample turns black and stops
smoking!

Testing and iron pyrite crystal sample for surface gold "may" have merit. I would certainly like to try it myself. If I come across
a sample of iron pyrite I will try it and report back. Hmmm.... I used to live on the CDN shield, greenstone belt and iron pyrite
as well as chalcopyrite was everywhere. Everyone had huge pyrite crystal samples at home and at school. Maybe time to call in
some pay back time debts. Besides maybe the old fart classmates and neighbours would like to advance prospecting science.
A good winter project!

The Delos Toole gold test method in the referenced link was written in 2000. Much has changed since them especially for the
procurement of chemicals. HCl (Muriatic Acid) is easy to get at the local hardware, but Nitric Acid is on the "banned list" and
impossible to get unless one has a business, is a University, Research Institute, the  gov, etc. and then documents and permits are
needed. The Delos Toole method should be completely rewritten to update it, include alternative and better less toxic leachate,
better sample preparation and a section dealing with pyrites and chalcopyrite samples. Maybe if I get a "round tuit" I will rewrite
the test if someone else does not do it!

 :)

GollyMrScience:
As you can see - more than one way to skin a cat.
Pals post does raise an important  point that you needs to be remembered. Different people use different terms for the same thing and it is important to make sure you are talking about what you THINK you are talking about.
Case in point:
Pal said "Getting back to the Delos Toole article and method for gold testing, the method probably worked just fine for Toole and may
others who were testing possible gold ore samples. Toole referred to testing ore concentrates, which "used to mean" to anyone
familiar with the mining industry, to be the crushed and milled ore samples ready for the leaching plant or the smelter, not
the chunky bits of rock with waste. Toole should have been more clear and specified a crushed, milled and well mixed ore sample -
the concentrate."

Very good point as people who work in the industry use terms like "processed sample"and "concentrate sample" etc to mean different things.
A processed sample might mean concentrated by physical or chemical means or it could mean just run though a grinder.

Some call it a treated sample if chemistry is used and concentrate if physical. Or you can have a multi step processed sample with concentration and treatment.
Whatever the terms applied it is important that you be able to translate whatever result you get back to the original sample for a realistic evaluation of mineral content. It is also very important to know what the heck the other guy means as he describes what he did to the ore and you the same for him.

Yukon Digger:
I've sometimes had good luck crushing the sample, putting it over a fire/coals in an old pan for a 1/2 hr or so then cool it, recrush it fine and pan it out.  A 6 inch chunck of 4" dia steel pipe with a plate welded on the base and a 3/4 " steel rod for a crusher is fine. Those old Canadian Shield prospectors had pans at camp but never for placer. Glad I got to work with some of them when I was cutting my teeth.

I'd forgotten about the SnCl2 thing. This is  a great site for learning new stuff and for jogging the old memory banks.

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