Silver + Base metal ore

[Blakey]

Hi All,

I have an ore stockpile which I assayed and it contains:

• 843ppm Ag
• 5.2% Zn
• 1.3% Cu
• 9000ppm Sb
• 1520 Pb
• 2.7% As
• 5% Sulphur

I haven't tried roasting yet and have tried smelting the concentrate using fluxes. The first attempt I added an Iron rod to the crucible to help reduce the sulphur but the metal in the cone mold was hard and my magnet stuck to it so likely mostly iron.
The second and third attempt using limited and then no iron and only fluxes did produce a metal cone which had a lead tip and a zinc base. I cupelled the lead and there was no silver so I dissolved the zinc in nitric and then attempted to precipitate silver and got no silver. The fluxes I was using was a combination of Silica, soda ash, niter, borax.
So I can only assume the silver is in the slag.
Any ideas why my silver is not coming out?

Cheers!

 

[Yggdrasil]

Hi All,

I have an ore stockpile which I assayed and it contains:

• 843ppm Ag
• 5.2% Zn
• 1.3% Cu
• 9000ppm Sb
• 1520 Pb
• 2.7% As
• 5% Sulphur

I haven't tried roasting yet and have tried smelting the concentrate using fluxes. The first attempt I added an Iron rod to the crucible to help reduce the sulphur but the metal in the cone mold was hard and my magnet stuck to it so likely mostly iron.
The second and third attempt using limited and then no iron and only fluxes did produce a metal cone which had a lead tip and a zinc base. I cupelled the lead and there was no silver so I dissolved the zinc in nitric and then attempted to precipitate silver and got no silver. The fluxes I was using was a combination of Silica, soda ash, niter, borax.
So I can only assume the silver is in the slag.
Any ideas why my silver is not coming out?

Cheers!

There are 0.0843% Silver so which is 84 0.8 grams in a Kilogram.
Anyway there are significant amounts of Arsenic so I'd be careful with the out-gassing/smoke.
How much are you smelting at a time?

Edit to add.
Slight calculation error.
0.843 grams of Silver per Kilogram
Which amounts to slightly below 1 USD per kg or per 2.2 pounds
I'm not sure it is worth it.

 

[Blakey]

There are 0.0843% Silver so which is 84 0.8 grams in a Kilogram.
Anyway there are significant amounts of Arsenic so I'd be careful with the out-gassing/smoke.
How much are you smelting at a time?

Edit to add.
Slight calculation error.
0.843 grams of Silver per Kilogram
Which amounts to slightly below 1 USD per kg or per 2.2 pounds
I'm not sure it is worth it.

Its 2.71 troy ounces per 100kg pre concentration. And the ore is heavy so volume wise its not that much. At the moment my smelts are not that big, about 2kg of concentrate at a time until I get it right then ill go up a lot (I have big furnaces). My math says 2kg of concentrate (6kg of ore turns into 2kg of sulphide con) should yield about 5g of silver.
My economic endeavors revolve around my gold mining and processing and silver processing through electrolytic cells which I then sell to jewelers as 999 fine shot. Images below.
Getting this silver out of this ore is just for fun not for profit.

 

[Blakey]

So my current thinking is the silver is in the slag and I'm not reducing the sulphides enough. So do I need to add more reducing agent to liberate the silver? I am not sure why when I added iron it didn't reduce the sulphides and I ended up with an iron cone after the pour
Anyone successfully done a base metal smelt for silver and could perhaps explain chemically why its not working? and perhaps a rough ratio of flux agents I would need for this ore based on its assays?
Any help would be greatly appreciated.

Cheers

 

[Yggdrasil]

So my current thinking is the silver is in the slag and I'm not reducing the sulphides enough. So do I need to add more reducing agent to liberate the silver? I am not sure why when I added iron it didn't reduce the sulphides and I ended up with an iron cone after the pour
Anyone successfully done a base metal smelt for silver and could perhaps explain chemically why its not working? and perhaps a rough ratio of flux agents I would need for this ore based on its assays?
Any help would be greatly appreciated.

Cheers

The important thing next to converting the ore properly is to allow it enough time and have a thin enough flux to let the Silver properly mix and collect in the Lead.
With a 2Kg smelt you will have roughly 1.6 grams of Silver.

 

[Blakey]

The important thing next to converting the ore properly is to allow it enough time and have a thin enough flux to let the Silver properly mix and collect in the Lead.
With a 2Kg smelt you will have roughly 1.6 grams of Silver.

2kg of ore would give roughly 1.6g of silver but the concentrate should be about 5g. 100kg of ore crushed and concentrate gives me a con of about 33kg.
I think due to the reactivity of zinc the silver will end up there and not the lead, but if it did end up in the lead that would make my job easier in the final recovery. I can try leaving it in the furnace for longer to make sure the silver is effectively scavenged but it think my main issue is the liberation of the silver. Do you have a recommendation for potential flux ratios?

Cheers

 

[Yggdrasil]

2kg of ore would give roughly 1.6g of silver but the concentrate should be about 5g. 100kg of ore crushed and concentrate gives me a con of about 33kg.
I think due to the reactivity of zinc the silver will end up there and not the lead, but if it did end up in the lead that would make my job easier in the final recovery. I can try leaving it in the furnace for longer to make sure the silver is effectively scavenged but it think my main issue is the liberation of the silver. Do you have a recommendation for potential flux ratios?

Cheers

If you have Silver in Lead the Zinc may dissolve the Silver and create a dross that may report to the slag, or not, the Silver is 100 times more soluble in Zinc than Lead.
Maybe you need to treat the ore with a temperature high enough to burn off the Zinc,
I suspect it will give losses though.
How do you deal with the Arsenic?