Purple of Cassius- False Positive

[PeterM]

I get this hit, is it gold or a false positive, I am working on a complex gold ore, the photos provided shows me this when I add a drop of Stannous Chloride solution to my pregnant chloride solution. Oddly the hit will disappears after a while but I can make it reappear with a drop of barren AR. Possibly, I have too high of an ORP. My thoughts are the AR will momentarily pull the gold into stability but will not keep it there for long. Any thoughts guys? I need help!!!!

 

[FrugalRefiner]

Maybe it's just my monitor, but I don't see any purple, just yellow.

Dave

 

[PeterM]

Seriously?

 

[Eamonn]

It dosn't look purple to me either.

 

[Lino1406]

Stannous chloride test is not a proof for gold

 

[patnor1011]

How did you treat ore prior to leaching?
What other metals are present, what did assay found?

 

[PeterM]

Fellas, I am dealing with a very concentrated solution keep that in mind.

 

[solar_plasma]

Do you see any purple stain on those white spoons, when you dry them while the test is still positive?

Btw do you have an excess of oxidizer in there?

@Lino, purple stain would be pretty specific for gold, wouldn't it?

 

[FrugalRefiner]

Since you're dealing with an ore, I've moved this topic to the Prospecting, Mining, Ore Concentrates & Geochemical section in the hopes you'll get more helpful answers.

Dave

 

[goldsilverpro]

Doesn't look "gold purple" to me either.

 

[g_axelsson]

Try to denox it before testing.

Though, doesn't look as positive to me. Have you tested your stannous lately? Do you get a positive if you add a bit of gold chloride to your sample?

Göran

 

[jason_recliner]

Fellas, I am dealing with a very concentrated solution keep that in mind.

In a spoon, I would expect a typical positive stannous test of a very concentrated gold solution to be black.
You're more likely to see purple by combining a single drop of each on absorbent paper. The more consistent you can make your tests, the easier they will be to discern.

 

[PeterM]

Fellas, I am dealing with a very concentrated solution keep that in mind.

In a spoon, I would expect a typical positive stannous test of a very concentrated gold solution to be black.
You're more likely to see purple by combining a single drop of each on absorbent paper. The more consistent you can make your tests, the easier they will be to discern.

It this what your referring too?

 

[patnor1011]

How did you treat ore prior leach? Did you roast it sufficiently enough? What other metals did assay found present in that ore?

 

[PeterM]

How did you treat ore prior leach? Did you roast it sufficiently enough? What other metals did assay found present in that ore?

Yes sir, a chemical pretreatment but no roast. No, it doesn't fire assay because of the Se, and Te present.

 

[PeterM]

Try to denox it before testing.

Though, doesn't look as positive to me. Have you tested your stannous lately? Do you get a positive if you add a bit of gold chloride to your sample?

Göran

The Stannous Chloride is fresh, I make it often.

 

[solar_plasma]

Drive off any chlorine first. Try again.

If nothing helps, cementing on copper powder, filtering and dissolving this cleaner probe might be a way to go. If it is still negative I doubt there is any gold in this solution. Disclaimer: I have no clue about ores.

 

[Grelko]

because of the Se, and Te present.

What would the chances be, that the Selenium in this ore, could have become selenic acid? It'll dissolve gold also (gold III selenate), and is there a chance that this could be holding it in solution? https://en.wikipedia.org/wiki/Selenic_acid

Edit - This may be of some interest also, and added page numbers.

The Chemical News and Journal of Physical Science, Volume 86

Action of Tellurium and Selenium on Gold and Silver salts

Pages 309-311

https://books.google.com/books?id=8xlLAAAAYAAJ&pg=PA309&lpg=PA309&dq=selenium+aqua+regia+gold&source=bl&ots=5MTHGIKr2A&sig=S8O-XOlWSxC0GiN3I42awNe9KxI&hl=en&sa=X&ved=0ahUKEwiamaCTuqbKAhUGLyYKHQzGB24Q6AEILDAD#v=onepage&q=selenium%20aqua%20regia%20gold&f=false

Another edit - reworded

Fellas, I am dealing with a very concentrated solution keep that in mind.

Gold (III) Selenate
Properties - small yellow cryst; decomposes in light
solubility - i, H2O, s H2SO4, HNO3

Look at the very first post, picture 2, spoon on the right. if you zoom in, it looks like yellow crystals. Did you get rid of the extra nitric?

 

[PeterM]

because of the Se, and Te present.

What would the chances be, that the Selenium in this ore, could have become selenic acid? It'll dissolve gold also (gold III selenate), and is there a chance that this could be holding it in solution? https://en.wikipedia.org/wiki/Selenic_acid

Edit - This may be of some interest also, and added page numbers.

The Chemical News and Journal of Physical Science, Volume 86

Action of Tellurium and Selenium on Gold and Silver salts

Pages 309-311

https://books.google.com/books?id=8xlLAAAAYAAJ&pg=PA309&lpg=PA309&dq=selenium+aqua+regia+gold&source=bl&ots=5MTHGIKr2A&sig=S8O-XOlWSxC0GiN3I42awNe9KxI&hl=en&sa=X&ved=0ahUKEwiamaCTuqbKAhUGLyYKHQzGB24Q6AEILDAD#v=onepage&q=selenium%20aqua%20regia%20gold&f=false

Another edit - reworded

Fellas, I am dealing with a very concentrated solution keep that in mind.

Gold (III) Selenate
Properties - small yellow cryst; decomposes in light
solubility - i, H2O, s H2SO4, HNO3

Look at the very first post, picture 2, spoon on the right. if you zoom in, it looks like yellow crystals. Did you get rid of the extra nitric?

Tushay Grelko, Thanks for the info. FYIP: I use Urea to expel the Nitric while the preg is hot (Red-Brown nitrus fumes occur). I'll study the links. Keep it coming!!!

 

[Anonymous]

Those first pics where you point out that it's "a very concentrated solution." That's not overly concentrated to be honest and I mean that in the best possible way.

Just as a jokey aside- tushay is actually a french word - touché 8)

Good luck with it.

Jon

Edit: In light if the fact you're talking about mining Peter, and I'm normally looking at tests from concentrated e-scrap my comment above needs to be put into context. 8)