Smelting shaker and float cons

[dkbinco]

Greetings all, I worked the winter part time in CC at a friends 600 acre gold mine and have a fair amount of cons that I want to smelt rather than run through the aqua regia. All underground except crusher line. Anyhow there is 2 mills, two 12 foot shakers, a 3rd mill and 2 flotation troughs. the ore running was around 1 to 3 opt, the table cons were around 15 OPT and I don't know about the float cons, anyhow I have researched the flux's I have a fair idea of how to proceed and make my own after a few loads and cupil, watch the matte and fine tune with other flux's. I don't think I should use the recipe they use in their assay lab. I believe I should roast all of this stuff, the mine sends there's off in super bags to Nevada, but I know this is full of metal with gangue minerals like galena, arsenopyrite, breccia and tellurium, didn't see all the reports, mostly using the XRF. I guess I am asking for any advice, I am new to smelting and waiting on my furnace, slag mold, a few chemicals, and silica sand. I am not sure about the nail in the charge if I am roasting, or using latharge as a collector. And if the lead (II) oxide PbO is even ok to use. I am not a chemist, but I read Hokes and spend a lot of time researching them and processes, U tube, and others, but I want to do things right and safely so if I sound green don't yell at me...HA! I will appreciate any support. Thanks.

 

[SRM]

Lots to unpack here....I will take a stab at it, but I am sure others will chime in with better advice.

1) Good call NOT applying aqua regia to ore or concentrates especially with the sulfides mentioned.
2) Table cons can be Au/Ag rich in the #1 port and sulfide rich (galena and arsenopyrite, less precious metal) in the #2 port depending upon your table setup. I have never tabled Te minerals, so I do not know where they report.
3) Flotation cons (my guess is a rougher and scavenger, no cleaning) will be sulfide rich.
4) Smelting of sulfide cons without proper equipment to protect yourself AND the environment will not only get you in serious trouble, it will also have repercussions for your friend. Colorado has a dim view of mining and that is one bear you don't want to poke. What is your plan to mitigate the metals in the smoke?
5) The same comments apply to roasting
6) Some smelters use lead concentrates (galena) as their collector while assay labs typically use litharge. If a smelter uses galena, they normally just ensure there is enough scrap iron in the melt to mitigate the sulfides. General rule is to add iron if sulfides could be present.
7) A collector metal will increase your gold recovery and allow you to cupel as the first refining. The metal buttons produced by cupelling are appropriate for hydrometallurgy for further refining.

Think carefully before proceeding.

 

[dkbinco]

Thanks, I roast in a skillet 40,000 btu stove and blow air over it and I live rurally. I have safety equipment. I bought basic leathers, tongs, and have face shields and respirators with good filters and some welding gloves. Nobody can smelt commercially in CO. because of the EPA, but I am not a gold mine.
So are you saying to start I could just use a Chapman flux with thinner and throw some nails in the melt and see what settles at the bottom, because there is a bunch of pyrite for sure. I am not 100% on how much galena. And still roast first? I expect to find tune the recipe doing some small charges, well that's what I'm seeing.
Is it a standard practice to refine the smelted gold with sodium cyanide (witch I know nothing about) or chlorination with the aqua regia?

Thanks SRM, I appreciate it.

 

[SRM]

If it were me and I could do it safely (both personally and environmentally), I would roast before smelting. Chapman flux is a known, repeatable flux. If you don't like the results, crush and modify the flux based on the slag. Be careful with thinner, it usually eats crucibles. If you don't have much galena you may need to add a collector metal.
Most mines I have been around simply try to produce a saleable product such as a dore (from a cyanide leach) or a concentrate (from flotation). It is easier to let the specialists refine the material. I am sure others are better informed on commercial refining processes.

HTH....SRM

 

[dkbinco]

very good to know, thanks. We were sending probably 3000 lb super sacks of table cons and float cons to Nevada to process, half a flatbed at a time. If I don't like the yield or if it gets a matte or something I will crush up the slag and try again. I only have 50 lbs or so of each so I learned the aqua regia process and want to learn this too. I appreciate your support and will be back along the way. So what is your hobby my friend.