What to do with Aluminum oxide mud after AR

[bhilton]

I have done a few rounds of incinerating jewellers sandpaper and leaching base metals and eventually moving to AR.

Filtering is a pain but I am getting decent yields of gold.

Despite my effort to get all the pregnant AR filtered out, I believe some pregnant AR is still trapped in the mud.

Once I have a stock pile of the mud, what method can I use to try and get any gold out of it?

Thank you all!

 

[4metals]

Aluminum oxide is also known as carborundum and it is used as a grit on sandpapers used by jewelers. The structural form of carborundum contains deep cracks and the material itself is very hard. Because of this it is a great grit (it is also inexpensive) but for refining it there are 2 issues. First the deep fissures "lock" the gold in the cracks making it difficult for the acid to penetrate and those same cracks make it difficult for the "pregnant" acid to be rinsed free.

You will get better yields if the material can be crushed to a finer mesh in a ball mill, this eliminates a good amount of those crevices that are causing issues. After you get most of the gold out, melting the residues in a crucible with cryolite will dissolve the carborundum. This is not a quick and easy melt and often takes hours.

 

[bhilton]

Aluminum oxide is also known as carborundum and it is used as a grit on sandpapers used by jewelers. The structural form of carborundum contains deep cracks and the material itself is very hard. Because of this it is a great grit (it is also inexpensive) but for refining it there are 2 issues. First the deep fissures "lock" the gold in the cracks making it difficult for the acid to penetrate and those same cracks make it difficult for the "pregnant" acid to be rinsed free.

You will get better yields if the material can be crushed to a finer mesh in a ball mill, this eliminates a good amount of those crevices that are causing issues. After you get most of the gold out, melting the residues in a crucible with cryolite will dissolve the carborundum. This is not a quick and easy melt and often takes hours.

Thanks 4metals.

I've read that Aluminum oxide / carborundum has an extremely high melting point.

Could I take the incinerated and ground up ashes BEFORE doing an AR treatment and melt them with the right mix of flux / lead / etc to separate the gold from the carborundum? I don't mind if the base metals stayed alloyed with the gold, it would be easy to deal with that later.

I just think there has to be a better way than incinerating the sand papers, grinding them up with mortar and pestle, doing a nitric bath (or copper II chloride bath) to remove as much base metal as possible, filtering off the nitric or copper II chloride, then putting the mud through a hot & long AR simmer, then filtering again, which is ridiculously tedious...

I'd like to just take the ground up ashes and melt/smelt/cupel - I'm not familiar with those types of methods, but I would love some direction so I can research it.

I also wonder if I could put the ashes into an electrolytic cell to separate the gold?

Thanks,
Bill

 

[anachronism]

One pertinent question would be how much of it are you talking about? I do recall the original thread you made about this but if you could remind me as to how much it would be useful.

 

[Yggdrasil]

I have done a few rounds of incinerating jewellers sandpaper and leaching base metals and eventually moving to AR.

Filtering is a pain but I am getting decent yields of gold.

Despite my effort to get all the pregnant AR filtered out, I believe some pregnant AR is still trapped in the mud.

Once I have a stock pile of the mud, what method can I use to try and get any gold out of it?

Thank you all!

Is this a new batch or the same batch as before?

 

[Alondro]

Aluminum oxide is also known as carborundum and it is used as a grit on sandpapers used by jewelers. The structural form of carborundum contains deep cracks and the material itself is very hard. Because of this it is a great grit (it is also inexpensive) but for refining it there are 2 issues. First the deep fissures "lock" the gold in the cracks making it difficult for the acid to penetrate and those same cracks make it difficult for the "pregnant" acid to be rinsed free.

You will get better yields if the material can be crushed to a finer mesh in a ball mill, this eliminates a good amount of those crevices that are causing issues. After you get most of the gold out, melting the residues in a crucible with cryolite will dissolve the carborundum. This is not a quick and easy melt and often takes hours.

Carborumdum is silicon carbide. Aluminum oxide is alumina in the powdered form and CORUNDUM as the crystalline gem form, with trace metal dopants creating sapphire and ruby. Corundum is the SAME material used to make the alumina crucibles, because of its high melting point of 3,762F.

 

[FrugalRefiner]

Carborundum is silicon carbide.

Corundum is aluminum oxide.

Ruby and sapphire are corundum.

Dave

 

[snoman701]

I just save it. I think I've got a little over a five gallon bucket full at this point, not much. At some point I'll send it off for assay / pay as a low grade prepared sweep.

 

[Yggdrasil]

Carborundum is silicon carbide.

Corundum is aluminum oxide.

Ruby and sapphire are corundum.

Dave

I noticed my mistake and deleted the post.
Edit to add: This is one of the challenges on working on a phone.

 

[Yggdrasil]

SiC are soluble in molten NaOH or KOH

 

[4metals]

I'd like to just take the ground up ashes and melt/smelt/cupel - I'm not familiar with those types of methods, but I would love some direction so I can research it.

The question Jon posed is valid, it depends on quantity. Typically I saw the sand papers mixed in with bench filings so they were mixed with other materials and usually came in for a melt. That was because most jewelers expect lots they hand carry in containing visible gold filings to be melted so they can take a sample. These lots had a percentage as sandpaper but enough other metals to melt into a pool. Invariably these melts always yielded more values when the slags were re-melted with a collector metal. They were melted with a flux containing fluorspar but never got the long molten soak that a cryolite smelt would give.

If your lot has just sandpaper I would burn off the paper and crush it as fine as possible before a long soak cryolite melt and skip the aqua regia entirely. Your option now would be another melt with fluorspar and a collector metal.