Recovering values from borax slags

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L

Lobby

Well-known member
Joined
Jan 25, 2011
Messages
194
Location
San Antonio, TX
Hi folks,

I hadn't posted in awhile. But here I am with a question for ya'll.

To refresh your memories, I have a scrap gold business. Prior to selling my Au to refiners, I melt and analyze with my XRF. I've found a very reliable refiner, but I still check as errors can be quite a bit of money.

Ya'll know the drill:

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I use anhydrous borax as the flux when I melt, then remove the slag (frozen, dirty borax) from the bar. Mechanically (hammer), and through pickling (warm Sodium bisulfate in a crock pot).

I've not been disposing of the slag and I've felt there's some values in it. I have no idea how much.

Can ya'll advise as to how much gold, etc there might be in the slag? Whether it's worthwhile to keep it as I have? and how to recover it?

Should I just send it to a refiner, or is there perhaps a modification of an litharge assay process I can use to recover?


Thanks!
 
Others may come along with better advice,

I crush or grind the slag glass to fine powder screen and pan, then I would melt the slag again this time, add a metal as a collector copper, or silver or lead, the slag crushed to powders and these metals could be mixed as filings, flakes beads or even as powders (like litharge PbO for lead) adding more flux, a little borax, sodium carbonate, something as a reducer like a little flour, tiny bit of fluorspar.

I know this was discussed in length on the forum I just do not remember where, but I would bet if you could find it, there will probably be a good recipe for a flux for the slag glass.

You will also want to use a cone mold.
 
If it were gold i would tell you to go for it. Being how it's silver it's a little different. How much slag are we talking? It takes a lot of silver to justify what processing it would take verses gold. With mine (gold) i just grind it in a pestle and run it through nitric acid to break down the flux. Then on to ar.

Butcher has given great advice for the melting route. Me i just do things a little different. :lol:
 
:mrgreen:

Actually, the bar only looks like silver. It's actually about 5 or 7 ounces of gold. If I recall correctly, it was a camera photo, whereas the others were a better camera.

I normally don't bother melting and assaying silver jewelry, as it's just not that much $. So the slag I've got is gold slag. I don't have that much, but as a matter of good lab practice, I've been keeping it. I plan on getting a stainless pan with a small anvil to hammer the slag off the crude bars, thus allowing me to catch the slag.

In my head, I'd come to a conclusion like Butcher suggested. Thanks for that, by the way.

I just thought I'd float the topic.
 
Palladium said:
If it were gold i would tell you to go for it. Being how it's silver it's a little different. How much slag are we talking? It takes a lot of silver to justify what processing it would take verses gold. With mine (gold) i just grind it in a pestle and run it through nitric acid to break down the flux. Then on to ar.

Butcher has given great advice for the melting route. Me i just do things a little different. :lol:
Click to expand...


Do you get much gold when you run it through Nitric?

By the way, I'd never had thought of that. (we need a clap smilie)
 
Crushing the slag helps with recovering the bigger "pieces" of gold and stones. Boiling in dilute sulphuric will help to free and spot the smaller pieces.

Here's some more posts on the subject:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=12632&p=125892&hilit=boiling+in+sulphuric#p125892
Take care!
Phil
 
Lobby said:
Palladium said:
If it were gold i would tell you to go for it. Being how it's silver it's a little different. How much slag are we talking? It takes a lot of silver to justify what processing it would take verses gold. With mine (gold) i just grind it in a pestle and run it through nitric acid to break down the flux. Then on to ar.

Butcher has given great advice for the melting route. Me i just do things a little different. :lol:
Click to expand...


Do you get much gold when you run it through Nitric?

By the way, I'd never had thought of that. (we need a clap smilie)
Click to expand...

It's all really according to how much gold is their to start with, but i get it all with this process and then ar. Sulfuric works well also i just hate even messing with the stuff verses nitric.
 
My suggestion is that when you accumulate some slag or what I like to call flux from gold melting, you put it on a coffee pot and boil vigorously for hours. Once in a while pour out the cloudy liquid (making sure you do not throw out any solids) and re-fill with water. Keep the boiling going until you see finely divided stuff. The flux will break up into small pieces. Sometimes you can break up the larger chunks after they boil for a while and then continue boiling. I would use tap water. After a while pour the water out, put the solids in a large dish and examine what you have. You may find diamonds, other stones and small beads of gold. You can then decide if it is worthwhile pursuing.

My experience is with processing via induction melting. Diamonds survive the process and can be recovered and you can accumulate significant gold after millions of dollars worth of melting. Once you have gotten the flux into small pieces and you see what you have, you can pick the stones out or some of the gold beads, you will also see zillions of little springs and other things you can pick out with a magnet (although be careful because they may be coated with gold or have little gold beads attached to them which you can see with a magnifying glass). Then, you can simply inquart the metal beads (gold) with silver and then refine.

I recommend you NOT treat the flux with acids right away. It makes a mess of hard to filter gooey stuff, it is very inefficient and not as simple and clean as boiling the flux first.
 

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