flux recipe for smelting fines

[douglas23]

Hi everyone,
My first post here, hope it's not a dumb question . Having read most of Hoke's book and spending half the day searching the forum for an answer I have not found what I'm looking for > I have about half an ounce of gold fines about 90%+ in purity that were dredged up by a local miner here in Alaska. I'm a jeweler and I would like to make it usable for making wire and bezel strip for stone setting. I don't need absolute purity, 22k is good enough, but I do need it to be workable and not brittle. Previous attempts at melting performed by the miner resulted in a very brittle porous material that is useless for making anything but cute little granules. I've been informed that iron or other base metals are likely the cause and that I need to use a flux containing sodium nitrate as an oxidizer along with silica or glass and borax. I am very familiar with melting, I cast silver all the time, and I have an electric melting furnace with a graphite crucible. My question is what is the ratio of saltpeter:borax:silica, is a broken glass jar ground up into little bits ok to use? are there any other ingredients I should add, and how much should I use for half an ounce of material?

Thanks,
Douglas

 

[butcher]

douglas23,

Gold or even silver can be cleaned up a little bit (slightly) in a melt with flux, but in reality the improvement is only minor basically, and even if you tried it with the placer gold you still would most likely not improve the gold to make it workable enough to make jewelry out of the impure gold.

The gold needs refined.

Hoke's book will describe the flux used to improve the gold in a melt.
But more importantly her book will help you learn how to refine your gold.

Hoke's book can be found in the book section or links in many of the members signature lines.

 

[4metals]

Another option is to semi-refine it;

I think the easiest and the best option based on your needs would be to melt the concentrate with borax, soda ash and some fluorospar to make a nice thin slag that will not hold up any beads, then remelt and inquart with some scrap silver. Now a simple parting with nitric will give you a 98-99% pure gold and the other base metals in the mix will be in solution along with the silver. The higher purity of the gold will make working it easier and you can alloy it to whatever you wish for karat. The silver in solution will cement out on copper wire and give you 99% pure silver to use the next time you need to inquart.

I know quite a few jewelers who use this process to clean up 10 and 14 karat scrap they buy to make "almost fine" gold for making alloy they need for use in their shop.