Mystery mineral in my concentrates

[BentFunky]

I have a mystery in my concentrates.

Ok, what mineral is very bright and metallic looking? It's not affected by roasting, warm nitric acid, or warm aqua regia. Not as heavy as gold but still among the heavier bits of material in my concentrates. Doesn’t appear to be malleable and might be brittle. Can't tell for sure given how small pieces are.

Characteristics are not consistent with pyrite, or similar. Seems to have characteristics consistent with some of the PGMs. However, there's a lot of it and I'm just not that lucky.

Any thoughts?

 

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[Jim in Idaho]

A good pic would help alot.
Jim

 

[smokeythecat]

Loellingite will do that. Its found in areas gold occurs frequently.

 

[Clay Diggins]

zircon

 

[BentFunky]

A good pic would help alot.
Jim

Appreciate the reply @jim in idaho. Looking for a macro lense.

 

[smokeythecat]

Your cell phone may do ok. Hold it horizontally to take the picture.

 

[BentFunky]

Loellingite will do that. Its found in areas gold occurs frequently.

@smokeythecat, initially thought that you nailed it until I read on mindat that Loellingite is soluble in nitric acid.

 

[BentFunky]

Your cell phone may do ok. Hold it horizontally to take the picture.

Buddy has a macro lense that fits on cell phone. Will pick it up tonight.

 

[smokeythecat]

What state was it found in? That makes all the difference.

 

[BentFunky]

I'd starve to death if I had to make a living with my photography skills . Just couldn't get an in focus pic. Target are just too small and reflective.

@smokeythecat, material found in southern MD. For now, I'm going with Occum's razor. Your answer is reasonable. Material is likely a sulfide or iron compound. It's appearance in post-roast and post-aqua regia concentrates could be due to inadequate time roasting and not enough nitric, respectively.

Outside possibility that some of what I'm seeing are PGMs.

Stannous Cloride tests on concentrates giving positive result for platinum. I've not dealt with PGMs before, so not sure how much confidence I have in those results. Assays on rocks in same area were positive for small amounts of gold and PGMs, so could be legit. (Concentrates were from panning, looking for placer gold).

I just ordered some chems online that will allow me to drop PGMs from aqua regia if present, so should be able to validate tests, sodium chlorate and ammonium chloride.

Appreciate all input!

 

[russau]

I have a mystery in my concentrates.

Ok, what mineral is very bright and metallic looking? It's not affected by roasting, warm nitric acid, or warm aqua regia. Not as heavy as gold but still among the heavier bits of material in my concentrates. Doesn’t appear to be malleable and might be brittle. Can't tell for sure given how small pieces are.

Characteristics are not consistent with pyrite, or similar. Seems to have characteristics consistent with some of the PGMs. However, there's a lot of it and I'm just not that lucky.

Any thoughts?

I would recommend the book "mineral identification " By Dr. Jim Madonna " He is a Geology Professor at the University of Fairbanks Alaska

 

[Bonaro]

In Washington I have seen this a lot. It appears silvery or white in the pan and usually plenty of it.
Get a strong magnifier and take a close look. The stuff I see is very fine crystals but not sure what kind. This would explain the resistance to heat and chemicals.

If you suspect PGM then divide out as pure of a sample as you can and pour some strong Hydrogen Peroxide over it. The H2O2 should result in a weak bubbling action.

 

[BentFunky]

In Washington I have seen this a lot. It appears silvery or white in the pan and usually plenty of it.
Get a strong magnifier and take a close look. The stuff I see is very fine crystals but not sure what kind. This would explain the resistance to heat and chemicals.

If you suspect PGM then divide out as pure of a sample as you can and pour some strong Hydrogen Peroxide over it. The H2O2 should result in a weak bubbling action.

@bonaro, thanks for the great tip re H2O2!

 

[BentFunky]

Mystery solved. Mineral is silver. There’s soooo much of it, it consumed all the nitric leaving a lot of silver remaining, so it appeared to me as though material survived nitric bath.

Decided I needed a redo.

I went digging today. Area had an even higher concentration of silver. See pic below.


Put a small amount of material in aqua regia (didn’t know it was silver at this point). Had to add nitric twice. First pic below is result in beaker. Took it off heat and let it cool. Tested with stannous chloride. Test sample immediately went milky white. Dead give away for silver. Second pic is aqua regia after putting it back on heat and then adding HCL. This precipitated silver chloride from solution.





I know what you’re thinking ... silver isn’t dissolved in aqua regia. Right? It would if all the HCL was consumed while still having a good amount of nitric. Then, nitric dissolved silver.

Silver is cool, but gold and PGM are profitable!

The only thing that I don’t understand is that the material which is ostensibly silver was attracted to strong magnet (before test began). After I was done with test, I checked the remaining undissolved sediment. At this point it was not attracted to magnet. Can silver be locked up with a ferromagnetic mineral like magnetite?


Update:
Took about half a cup of concentrates in question and smelted it using Chapman's flux and silver as a collector metal. Got about an extra gram of silver/gold. However, slag had a thick layer of mat. So .... appears that I very well have values locked up in sulfides. Will crush, roast, and then re-smelt mat material to see if there is anything interesting.

Update2:
Also, looks like PGMs. Precipitated Pt, at least. Haven't tried Pd yet but suspect it's there as well.