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I used to visit an operation that processed spent carbon from cyanide based gold mines in Nevada. The carbon was burned, the gold collected in what was a gigantic fire assay, and the lead from the assay which would weight a couple hundred pounds was cupelled 25 pounds of lead at a time. It was pretty spectacular and it worked well to recover the precious metals left behind in the carbon.

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I recently smelted some "middlings" material from my shaker table that I was not expecting to get any gold from.  I used chapmans flux and thinner. (1.5 parts chapmans to concentrate/20% thinner to concentrate).  Premixed the material.  Ran it through the kwik kiln until a water like consistency was achieved, I poured it from a graphite cupell to a graphite conical mold.  This took around ten minutes or so.

 

After dumping the conical mold there was no gold at the bottom; like I said I wasn't expecting any.  Before I broke the slag I notice what looked like gold on the outer edges of the slag, mid height on the pour.  I then broke the slag apart and noticed that this gold looking material was only on one side of the slag/pour.  I examined this gold looking stuff with a 60x loupe;  it looked like unliberated gold attached to quartz, or just iron pyrite.  Neither of which even make sense.

 

When I poured I know for sure the mixture was hot enough as it instantly poured just like water or better.  With that said what could this gold looking material be?  Shouldn't all quartz and iron pyrite burn into black slag and that's it?  Am I smelting incorrectly?  Any ideas or thoughts would be appreciated.

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Pyrite does melt into a liquid and pour. No, the pyrite will not necessarily go into the slag the way that quartz does. Melted and re-solidified pyrite may be what you have. The easy test is to strike it with a hammer. Pyrite shatters, gold flattens.

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The iron goes into the "Slag". The copper, silver, gold is poured into an ingot.

That is not necessarily true. Often the iron, if present as sulfides goes to a melted sulfide material called matte, which does not mix with the slag - its like oil and water. If present as oxides, yes most of that iron will report to the slag.

 

Smelting by definition IS the process that separates the iron including pyrite from noble metals including copper, silver and gold.

No, that is not a good definition of smelting at all. Smelting is a pyrometallurgical process that extracts metals from its ores - no matter the metal, and smelting does not necessarily involve any "noble" or precious metals. Iron smelters produce iron - but produce no precious or "noble" metals. In iron smelting, iron does not go into the slag. Copper is a base metal, not a "noble" or precious metal. Many smelting operations produce a melted sulfide product often called a matte or other name.  Lead and zinc are commonly produced by smelting, even the electrolytic process that produces aluminum from melted materials is considered a smelting process. 

 

There is lots of info available on smelting, do some more research! The Ammen book has lots of info on precious metals, but is not a good guide to smelting generally.

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If you provide a definition of smelting that is wrong, then it is precisely and exactly wrong.

 

SO what then is a furnace of "reasonable quality" that is suited for smelting? What is not "reasonable quality"?

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Are any of you guys familiar to the iron nail method of smelting pyritic ore?  Thus avoiding roasting of ores?  Any first hand experience with this technique?

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