Jewelers polish papers

[bhilton]

I have a friend who runs a small jewelry goldsmith shop and he gave me a little pile of sand papers and cloths to try and process.

I believe the easiest way for me is to burn them up in a frying pan and then saturate the solution with water, let it settle a minute, decant of ash material a couple times, and finally I could treat it with some of my left over copper II chloride.

If i filter out the copper II chloride, could I move on to use AR at the next step?

Or what technique do you recommend?


Thanks!
Bill

 

[nickvc]

Incineration is definitely the first process but when dealing with such small particles of values I’d advise heating from below increasing the heat slowly to avoid values from blowing out of your dish.
Once you have done that unless you are expecting significant silver I would simply put into a beaker cover with HCl put it on a hot plate and add nitric in very small increments once the HCl is warm , do not leave on the heat for long periods without stirring to avoid hot spots which can and will break your beaker, keep heating the solution with stirring and once all reaction has stopped allow to cool filter and precipitate with the precipitant of your choice.
If done correctly you should recover 90%+ on the first extraction depending on volume of material.

 

[bhilton]

Incineration is definitely the first process but when dealing with such small particles of values I’d advise heating from below increasing the heat slowly to avoid values from blowing out of your dish.
Once you have done that unless you are expecting significant silver I would simply put into a beaker cover with HCl put it on a hot plate and add nitric in very small increments once the HCl is warm , do not leave on the heat for long periods without stirring to avoid hot spots which can and will break your beaker, keep heating the solution with stirring and once all reaction has stopped allow to cool filter and precipitate with the precipitant of your choice.
If done correctly you should recover 90%+ on the first extraction depending on volume of material.

It would be mostly gold and copper. Work done mainly on with 10k, 12k and 14k yellow gold jewelry. Small portion of work done white gold with nickel in the alloy.

I will incinerate on a frying pan from below and slowly, great advice.

Thanks!

 

[Yggdrasil]

It would be mostly gold and copper. Work done mainly on with 10k, 12k and 14k yellow gold jewelry. Small portion of work done white gold with nickel in the alloy.

I will incinerate on a frying pan from below and slowly, great advice.

Thanks!

Read Hokes book carefully, it was written specifically for these cases.

 

[snoman701]

You have to make sure it's dead burnt, not just charred. Otherwise it makes a horrendous mess.

Don't wash any ash away.

 

[4metals]

Are the items you call sandpaper made with a carborundum? Carborundum has a huge surface area with deep crevices that make it such a good abrasive. It is also what traps values in the refining process. The carborundum is mostly aluminum oxide Al₂O₃. It is used as an abrasive because its crystalline structure causes it to shatter with sharp deep fractures, which is why it is a good abrasive. The melting point of aluminum oxide is 2890ºC and gold melts at 1065ºC so gold particles are held in deep pockets of insulating aluminum oxide. Melting this material requires a flux using cryolite to dissolve the aluminum oxide.

Back in the day when I refined this material I always saved the insolubles from the refining process and melted them with a flux to actually put the abrasive material into liquid in the flux and therefore release anything it may be holding. I always recovered values even after long aqua regia reactions in heated reactors. This is after incineration and aqua regia processing. Eventually I changed the process to always melt the material after incineration to get all of the values.

You have a special case because the lot is so small, incinerate it and give it a long warm aqua regia soak to get the best recovery without melting. There will be values in the ash so put it all in acid.

 

[4metals]

I should add if you dry out the insolubles return them to your friend. He can add them to his sweeps burnables drum and any values remaining will be part of the sweeps.

 

[bhilton]

I should add if you dry out the insolubles return them to your friend. He can add them to his sweeps burnables drum and any values remaining will be part of the sweeps.

Thanks for your amazing details!

I had already burnt the sandpaper from my picture earlier. My friend has more so ill find out soon what brand and type of sandpaper it is.

After putting the ashes in warm/hot AR, I noticed during filtration a silvery like paste was clogging my filters up. I juggled filters and funnels to get what I feel is 90% of the AR solution through.

I set the sludge and filters aside for another day or like you suggest, give them back to my friend.

I precipitated with Smb after Sulfamic acid denox and holy cow that little bag of sand paper appears to have yielded 1.2-1.5 grams of gold powder! I have to pour solution off and wash it and refine again, but just looking at it, I really think itll be at least 1.2g.

So cool!

 

[kurtak]

Are the items you call sandpaper made with a carborundum? Carborundum has a huge surface area with deep crevices that make it such a good abrasive. It is also what traps values in the refining process. The carborundum is mostly aluminum oxide Al₂O₃. It is used as an abrasive because its crystalline structure causes it to shatter with sharp deep fractures, which is why it is a good abrasive. The melting point of aluminum oxide is 2890ºC and gold melts at 1065ºC so gold particles are held in deep pockets of insulating aluminum oxide. Melting this material requires a flux using cryolite to dissolve the aluminum oxide.

Back in the day when I refined this material I always saved the insolubles from the refining process and melted them with a flux to actually put the abrasive material into liquid in the flux and therefore release anything it may be holding. I always recovered values even after long aqua regia reactions in heated reactors. This is after incineration and aqua regia processing. Eventually I changed the process to always melt the material after incineration to get all of the values.

You have a special case because the lot is so small, incinerate it and give it a long warm aqua regia soak to get the best recovery without melting. There will be values in the ash so put it all in acid.

I couldn't have said that any better - now I don't need to right that post

The only thing I would add is that I would likely add a bit of silver cement to the smelt as a collector

Kurt

 

[kurtak]

Are the items you call sandpaper made with a carborundum?

From what I can see in the pic the sandpaper is most definitely aluminum oxide - so if smelting you most certainly want some cryolite as a part of your flux make up

Doesn't take much - "about" a teaspoon per cup of flux

Kurt

 

[4metals]

but just looking at it, I really think itll be at least 1.2g.

One thing I have never been good at is guesstimating from wet unmelted gold. Back when I did a lot of fire assays I would always get questions like "how much gold is in there". I quickly learned to tell them when it would be done for a good accurate answer.

As an wise old Romanian assayer who taught me a lot about assaying told me, "The balance never lies!" So I always held back my answers until I could weigh my gold on the balance.

 

[Spaceships]

Possibly a bit left field for some but I'd try a sample in Phosphoric acid before doing anything else to it.

 

[4metals]

Phosphoric acid does dissolve alumina but I have only done it on a sample prep basis for analytical work not as a pre treatment for refining.

I am a bit old school, at least the old part, but I prefer a melt approach to get all of the metal into a bar form before any recovery begins.

The phosphoric acid approach can digest the alumina but all of the values will be in the insolubles, generating more waste and a more difficult to treat waste stream.

But left field isn't necessarily a bad place to be.

 

[Spaceships]

Yeah I was thinking more along the lines of get rid of what you can before dissolving anything (edit) in AR. Done correctly the vast majority of the gold is going to be at the bottom of the beaker, which is why I suggested trying a sample rather than going all in on one approach. If it's messy then revert to "cook the heck out of it" however if done incorrectly that's going to have its own issues too.

I suppose I prefer "dissolve the heck out of it but selectively" to "burn it all with fire" and I recall your and Chris' sound advice in my early days which was to quickly learn which acids dissolve what, so that you know how to reduce the amount of things that you don't want in order to get at the values. As you said, different approaches!

 

[bhilton]

One thing I have never been good at is guesstimating from wet unmelted gold. Back when I did a lot of fire assays I would always get questions like "how much gold is in there". I quickly learned to tell them when it would be done for a good accurate answer.

As an wise old Romanian assayer who taught me a lot about assaying told me, "The balance never lies!" So I always held back my answers until I could weigh my gold on the balance.

haha, yea, I'm a beginner here, I probably shouldn't even be guessing, but guessing is fun!!

What's your preference on smelting- do you use a crucible, flux and oxy acetylene torch?

I also want to add,

There will be silver in the sludge I set aside, as it wouldn't be dissolved in the AR. I'll have to do some research on smelting that sludge and those clogged filters, separating aluminum, silver and the remaining bit of gold.

When I did my stannous test before SMB, I noticed the color would flash orange and then go dark grey/purple, indicating gold. After I added SMB and while precipitation was well on its way, I did another stannous test and it stayed orange, looks just like the pictures I see online of platinum orange. However, that was only 5-10 minutes after I put the SMB in. This morning after letting it precipitate for 12 hours, the stannous test shows no color.

Does that mean the precipitate could have Gold and Platinum in it or anyone have any ideas?

 

[bhilton]

Here is what it looks like this morning, I have to pour it off and wash it still.

 

[4metals]

I suppose I prefer "dissolve the heck out of it but selectively" to "burn it all with fire" and I recall your and Chris' sound advice in my early days which was to quickly learn which acids dissolve what, so that you know how to reduce the amount of things that you don't want in order to get at the values. As you said, different approaches!

Years back I use to refine for a thick film hybrid circuit manufacturer. He shipped in drums of thick film printed circuits on alumina plates. This alumina was not used as an abrasive but a substrate. But after the substrates were stripped of the gold with aqua regia the white substrates were tinted green. This indicated to me the solution was getting trapped in the alumina and holding values.

In this case phosphoric acid may have been the best choice because there were large quantities of substrate material just hanging things up. Phosphoric as pre treatment before aqua regia.

Our approach was melt with cryolite flux and copper collector. We waited to accumulate a full 55 gallon drum of the greenish substrates and fired up the big boy furnace. The result was a copper based bullion from the large quantity of copper added but the assays showed about 10 ounces of Gold in the bars. Copper cell feed!

 

[4metals]

What's your preference on smelting- do you use a crucible, flux and oxy acetylene torch?

you seem to confuse the term melting and smelting. You will be melting. For melting I prefer a torch for smaller melts and a crucible for larger melts.

 

[Spaceships]

Haha I hear you on the copper. I'm working on exactly that myself at the moment. Wrapping my head around the cell detail is interesting.

 

[4metals]

Does that mean the precipitate could have Gold and Platinum in it or anyone have any ideas?

SMB is very selective for gold leaving PGM's behind in solution. If the solution tested negative on standing there was no Platinum or Palladium to begin with in appreciable amounts. And considering the yield was slightly over 1 gram (yet to be accurately quantified) I wouldn't hold out much hope for any PGM's.