Using Shorinternational tester

[Anonymous]

Hi, I'm totally new to this stuff. I have an area on my property that is very geologically interesting and has all the precursors for gold formation. The ore is lightly variant but very mineralized, there are several quartz based gossans as well within the very immediate vicinity. I've also found a very large vein of what appears to be chlorite, layered with quarzite and pyrite immediately bordering one of the gossans. There is very very abundant pyrite within all of the surrounding ore as well. I also am under the firm belief that there is tellurium involved here. I've been taking different samples and doing the following with them:

-Crushing the samples down to a mineral flour sized particle (-300 mesh) to increase the surface area for dissolution of any gold
-Putting a small amount of the powdered sample into a small test tube and filling the test tube half way with Aqua Regia made with hydrochloric acid and nitric acid
-in an attempt to dissolve any gold that may be present, I leave this overnight in a room temperature environment and shake it periodically to stop the powder from caking on the bottom of the tube
-about 12 hours later, I take a sample of the solution from the top of the the mixture (to try not to get any particulate in the drops I use for testing)
-I then place 2-3 drops of this sample into a glass petri dish
-I test it by dropping 1-2 drops of the shor international Precious Metal Detection Liquid into it and I look for color changes as indicated on the bottle. I am guessing this is stannic chloride? You can see this product at the bottom of this page: http://www.shorinternational.com/RefinAcidinstr.htm
-In the samples that I would most likely suspect a gold content, I seem to be getting a very dark black color appearing instantly with this test. Many samples are also varying shades of black, and some are void of any color change.

My real question is whether this is anywhere near a valid method to test for the presence of gold. I'm sort of hoping that Harold will chime in on this one as well because he seems unbelievably knowledgeable and I read a posting by him talking about getting a black color from samples where tellurides were involved. I tested the method extremely generally by placing a tiny piece of shaved 18k gold into a blank solution of the aqua regia and did the test as usual. I got an instant jet black result from this. As well, is there any way to understand what type of concentration may likely exist in my different ore samples aside from sending these to a lab for something like a fire assay?

Sorry in advance if any of these questions are ridiculous. I guess we all have to start somewhere. :lol:

THANKS!

 

[lazersteve]

Petee,

Welcome to the forum.

Dilute the pregnant liquid with a few drops of water before adding the test solution and see if you get a purple color instead of black.

If the Shor solution is stannous chloride, diluted gold chloride solutions will show as positive as a purple color. If diluting does not lighten the color perhaps the Shor solution is not stannous chloride, but another gold precipitant that precipitates the gold in the form of a black powder.

If you can, make some stannous chloride of your own to be certain what your test solution is, this way you know what the results mean and what colors to look for.

Steve

 

[Anonymous]

Thanks Lazersteve,
I'll give that a try. Does everything else sound like it makes sense in terms of testing for the presence of gold in the ore? Any good straightforward methods to make the stannous chloride myself? Ive read some different things like using regular store bought soldering wire in conjunction with hydrochloric acid. Any tips of the proportions to get it right?

Thanks
-Petee

 

[lazersteve]

Thanks Lazersteve,
I'll give that a try. Does everything else sound like it makes sense in terms of testing for the presence of gold in the ore? Any good straightforward methods to make the stannous chloride myself? Ive read some different things like using regular store bought soldering wire in conjunction with hydrochloric acid. Any tips of the proportions to get it right?

Thanks
-Petee

Your process sounds like it should extract free gold from the ore if it were present. I don't see a problem with it being used for testing purposes. A fire assay would be a much more accurate and definitive route to determining the gold content if any is present.

There is a link in my signature line for making and using stannous chloride.

You should take a look at the Guided Tour Link also.

Steve

 

[Anonymous]

Well, no matter what I do, I still get a dark black color when testing for the same samples. There is something within some of these specific samples that is causing the dark black color reaction. Are there any metals that would produce results that would show dark black? I can't find anything on it. I get the same with my own brew of Stannous chloride as I get with the Shor international precious metal detection solution. That stuff must also be Stannous chloride.
If anyone has any suggestions on what would produce a dark black color, please post. I am super confused here.

THANKS!
-Petee

 

[lazersteve]

Can you post a photo or two of the solution and test results?

Steve

 

[Anonymous]

So here are some before and after pictures of the samples Ive been testing.

 

[lazersteve]

Looks a lot like iron in solution.

Place a few mL in a separate test tube, add a few drops of ammonium hydroxide and see if you get a red-brown precipitate (iron hydroxide).

Filter out the iron hydroxide and add a few drops of HCl to acidify the solution and test with stannous again.

Steve

 

[Harold_V]

I've never been a fan of attempting to extract values from ores using acid. It is generally a waste of time, and, in my experience, tests conducted by your method tend to be very unreliable. I'm of the opinion that even if you have gold present, it isn't likely to remain in solution by the method you are using now. Could be wrong.

You might give this a try. Do use a small amount, no need for more.

Roast your (crushed) material, exposing all of it to air to insure you eliminate sulfur. Heat to a dull red heat, and rabble well.

After roasting, wash the material with HCl, heating the solution.

Rinse well.

Roast again. (You may find there's some sulfur that has been exposed by the HCl wash)

Treat again with HCl.

Rinse well.

Now use a small amount of AR to dissolve any potential values. By now you should have eliminated sulfur, iron, and any traces of tellurium.

I processed a large amount of iron pyrite by the above method, which proved to be very successful. That which I processed was known to contain a substantial amount of gold, making it feasible.

By the time you have roasted and treated the pyrite, it will have been totally eliminated.

Harold

 

[Anonymous]

Thank you very much for the guidance here. I will try this over the next few days and post my results. I posted below another picture which is actually an AR solution that I had let dissolve for about 36 hours. Then I boiled it gently after which the solution turn neon orange, I separated it, and when I left it after separating it, a white translucent crystal film about a 1/8 inch thick lined the bottom of the container. I can't figure out what the white crystal layer is.

 

[lazersteve]

Still looks like iron to me.

The crust is likely some sort of salt. It may be soluble in water.

Steve

 

[Anonymous]

Your right! It is soluble in water. I just tried it. What type of salt could that be though?