Non-Chemical melting or seperating gold from fused silica

[Peg leg]

Newbie. I was pointed over here by a friend and am extremely exited to have found this forum.

I have a decent amount of gold (about an ounce) that is mixed with fused silica. I tried heating it with a torch in hopes that the silica would float to the top and be removed with Hydroflouric acid but I could never get it to melt enough for the glass to float up. Its very light small pieces of glass. Any suggestions on the best way to go about this? Wil a regular oxy-acetalene torch get hot enough to make the gold liquid???

 

[Anonymous]

crush the glass to fine powder and add some borax, soda ash(or washing/baking soda) to thin out the silica and lower the melting point.
Or you can crush to powder and recover the gold with leaching chemical process of your choice.

Jim

 

[Harold_V]

As has already been suggested by Jim, you can use soda ash to deal with the silica. It actually doesn't lower its melting point, although, in the end, it does yield a substance that melts at a lower temperature (glass). Molten soda ash dissolves silica. It is unlikely you would have success melting silica, which melts at a temperature in excess of 3,000°F. It would even be difficult to obtain a crucible that would tolerate the heat, but by using soda ash, overall temps are well reduced.

The amount of gold you have versus the amount of silica may create some problems in recovery If you choose to recover with heat. If you have a large amount of silica, it may be in your best interest to use a collector. Silver chloride added to the mix can serve to collect the gold, as could some cement silver. Either of them would serve to coalesce the values so they could be recovered. Best results are achieved by pouring the heat to a cone mold.

If you find the slag too viscous, with prills remaining, adding a small amount of fluorspar can serve to thin the flux, often to the consistency of water. However, it is correspondingly hard on the crucible, so use with discretion.

In this case, I advise furnace melting. Melting with a torch may not provide the soak time that would insure a good recovery. Hard to say. It would work, it's a matter of how well.

Harold

 

[Peg leg]

I was actually going to just leach the silica out with hydroflouric acid but the problem is that much of the silica is completly encased in gold. If I could just get the silica and gold to seperate I could leach it with the acid. Is this a flawed theory? I assumed that the silica would float on the liquid gold since it is so much lighter. It is probably a ounce of gold and less than a 1/8 ounce silica.

 

[eeTHr]

Peg leg;

You could be an educated chemist with lots of acid handling experience and a complete professional lab with all the safety equipment necessary to use hydroflouric, and if you are, just disregard this post please.

But if you are a good, optimistic, home workshop engineer, and you have read on the Internet that it will dissolve silica, here is my opinion: I wouldn't touch hydroflouric with a robot arm operated through a remote monitor/controller from the next county. 8)

If HF was the best or only way to do it, then Jim or Harold would have said so.

:idea:

 

[Peg leg]

I did not mean any dissrespect with my post. I am fully aware of the dangers of hydroflouric acid and I work with it on a daily basis in my job. However I am new to working with gold, which is why I posted the question about melting it the way I did. I like your analysis of not touching it with a robot arm. It is nasty stuff and can alter both your blood chemisty as well as can leach the calcium out of your bones just from the fumes, definatly not for the untrained. I wish I had a kiln or a furnace that would reach the heat required to make the gold liquid enough to flow together but the best I have been able to do Is make it all stick together in a big wafer and not really get liquid.

 

[eeTHr]

Peg leg;

Oh, I didn't see any disrespect in your post. It's just that whenever I see HF or lye mentioned casually, or something that could be explosive, I get an urge to toss a caution in there in case someone who is unfamiliar with these things happens to read it. I thought you probably knew what you were doing.

Molten soda ash dissolves silica.

Dissolving the silica, instead of melting it, could work for you. The torch you mentioned will melt the gold, and release the encased silica allowing it to be dissolved. I haven't done this exact process, but Harold would likely be able to answer questions about any specific step(s) of it.

Don

 

[butcher]

here's a suggestion use Harold's flux recipee, adding collector metal as suggested, smash and hammer and cut to smaller pieces, melt smaller portions with furnace or torch Acetylene oxygen in as an insulated inviroment as possible, heat these smaller batches stirring melt with the flame of torch, trying to get as much metals as possible to bead up, most of base metals will go into slag glass, values will collect to colector metals, depending on heat and flux, but you can end up with buttons or beads of values, if you added enough crushed glass or sand silica to melt, then crush this to powder in morter,smashing glass flux seperating beads for another melt, and then save for seperate batch, the crushed slag add flux for another melt of it also, then treating with acids of metals retrieved, I would not spend time dissloving silica with acid, I would go after the silver gold etcetera.

 

[Anonymous]

HF is not the way to go even if some of the silica was not encapsulated by gold.
Buy all rights if you chop the gold into smaller pieces you should be able to melt it and have the silica float to
the top, then beat with a hammper to remove the silica.
Butcher, that was a good suggestion.

Jim

 

[Harold_V]

It's always a good idea to give total disclosure, so others don't have to guess at your question.

Knowing that you have so little silica present, you should have good luck even torch melting.

Don't overlook the addition of soda ash. If you've ever melted platinum, you know that the temperature required is a brilliant white heat, so hot that it emits rays that burn skin. That's what you'd face trying to melt silica (assuming that's really what you have). Silica and platinum melt at roughly the same temperature.

I would personally avoid the use of HF, although if you are well experienced with its use, and can use it safely, it's possible it could be the solution in this instance, especially considering you have mentioned such a small amount of silica. In the end, melting with a small amount of soda ash and borax would yield good results.

Harold

 

[Peg leg]

First, where can I get the soda ash? I have the borax and I think I will go that direction first. I wasn't thinking in terms of melting the fused silica to begin with, I more thought if I could melt all the gold the fused silica would just float to the top and I could remove it but I can see where If I could melt it, that would be beneficial.

 

[butcher]

others may disagree but look at dish washer soaps for soda ash, works for me.
also action mining will have the flux's like soda ash
they are in sandy oregon and have a website, lots of other goodies there also.
http://www.actionmining.com/Catalog.PDF
http://www.actionmining.com/
glass silica usually on top of the gold if good hot melt.
and if hot enough and good flux mix, metals join in one button, not bunches of tiny beads mixed in glass slag

 

[AlanInMo]

First, where can I get the soda ash?

Swimming pool "Ph+" = Walmart and/or pool supply stores and of course Ebay.. :lol: (overpriced usually with shipping)

--> http://cgi.ebay.com/SODA-ASH-5-Poun...emQQptZLH_DefaultDomain_0?hash=item2c51913eb3

 

[eeTHr]

Peg leg;

The torch I was refering to was the oxy-acetalene, although a plain MAPP gas one will do it also.

Don

 

[goldsilverpro]

First, where can I get the soda ash?

From what I can find, Arm & Hammer "Super Washing Soda", found in the laundry section of most grocery stores, is about 85% sodium carbonate (soda ash). The other 15% is water. I also think Ace Hardware carries it. There is supposedly nothing else added (perfumes, etc.) This 85% percentage would make it the monohydrate, Na2CO3.H2O. The 15% water would easily be driven off by heat during the melting. Depending on where you buy it, the price seems to range from about $4.50 to $6.00 for 3.9 pounds - $1.15/# to $1.54/#.

 

[Peg leg]

Ok, here is another question. What is the best type of vessel to melt it down in and where can I find one? Up until this point in time all the melting I have done is in a stainless 200ml beaker but it is deep enough that the torch gets blown out because its so deep. I had some very small ceramic (maybe) or bone ash crucibles but the gold stuck to them and it broke them in half prying it out. I am thinking I might be best off to cut this into small chunks and melt it with the borax and soda ash into small buttons, easier to deal with and get to temperature.

 

[qst42know]

Be glad your torch went out in the stainless beaker. If it hadn't your question would be on separating a gold silica stainless alloy.

Lazersteve sells inexpensive melt dishes.

 

[AlanInMo]

Ok, here is another question. What is the best type of vessel to melt it down in and where can I find one?

Have you visited "Lasersteve's" website? You can watch his videos and buy a melting dish, all at one site..

:arrow: http://www.goldrecovery.us/site.asp

 

[Peg leg]

You guys have all the answers. Did I mention that this site rocks and I officially now have a new hobby that has very little to do with the gold and silica I already have. I really appreciate all the helpful advice and I will definatly let you know how it turns out with some pictures and the methods I used.

 

[Harold_V]

NEVER use unprotected metallic vessels to melt other metals. Molten metals are strong solvents of other metals, so you end up destroying the vessel and contaminating the material, to say nothing of losing values when they spill from the perforated vessel. At the least, you risk soldering your values to the vessel. In this case, a small melting dish, easily obtained from Lazersteve, would be the best solution to the problem.

Avoid deep vessels when torch melting. The reflected heat will be troublesome, as you've observed, and may even melt the torch tip when things go far enough south.

Be certain to season and prepare a melting dish prior to putting it in service. Otherwise they are subject to cracking. If you have no clue how to season a dish, ask here.

Harold