Recovering Any Valuable Metals From Unknown Metal(s)

[dcapone2004]

So, I have a few pounds of different (or maybe the same) unknown metal that I am trying to determine if any of it contains any precious/valuable metals. There is a descent chance, a good quantity of it is silver and maybe even some gold as the metal was left behind from a jeweler along with several pieces of finished jewelry.

The jewelry itself is sterling silver with rhodium plating (according to the markings). Additionally there are some gold plated pieces and some what I would venture to guess is brass molds.

The question is, since I officially have no idea what the metals may be (the majority of it is silver colored), what would be the best strategy to determine if any of it is silver or a silver alloy?

My thought process is to create shot out of it and heat it in concentrated (31, not 37 since it is a cheap starting point) hcl. If everything dissolves, well then it is fairly worthless. Alternatively, if there is remaining unreacted metal, there should be a fairly high confidence that the metal is silver or some type of silver alloy. Would this thinking be incorrect? What other silver colored metals would not dissolve in hydrochloric acid? Would any metals form a chloride with HCl that would instantly precipitate upon reaction that could help immediately identify what the metal may be?

From there, the plan was to rinse with distilled water and see what happens when exposed to nitric acid.

Is this plan ok? Is there a better way to go about this that would not be overly expensive (like buying an XRF analyzer)?

Thanks for any feedback.

 

[nickvc]

If you can get nitric it's very easy to check, you don't need gallons, but hydrochloric on its own will tell you little if the metal is silver.

 

[dcapone2004]

I can get nitric, but I can get a gallon of hcl at lowes for $8 quickly as an early test.

Also, I didn't want to go right to nitric as I think I would have contamination if say the metal is a mixture of zinc, magnesium, and silver.

If I treat it with hcl first, the zinc and magnesium, and iron, and probably some other stuff if there is any other stuff would be removed, leaving behind a more pure silver/valuable product if in fact there is any silver content.

However, I would be interested in hearing your thoughts of quickly being able to tell using nitric knowing that there could be numerous other metals alloyed in that could cause a mixture of nitrates to be formed.

 

[rickbb]

If you want a cheap spot test to see if it is silver you can order some small bottles of pre-packaged acid testing kits from ebay.

Would save you from getting gallons of acid in case you don't need it.

 

[dcapone2004]

I did do that and the results were very inconclusive. Produced a rainbow color so that is why I think the metal is fairly dirty.

I did melt some of it down into and ingot to mold it. It is not magnetic, so iron content is likely extremely low if at all and the density based on the weight of the ingot and the approximate dimensions (kind of hard to measure exactly) is quite close to silver.

I guess a better question may be, is there a downside in attempting to "clean" it in hcl first?

 

[METLMASHER]

First use a magnet on all of it. Any that is strongly magnetic is likely plated over steel or ferrous content. Any that is very slightly magnetic can still be plated, but you indicated you suspect Rhodium plating, so it may be of value, even if it's plated.

Then buy a dropper of Schwerters solution for silver testing the rest. Saves a great deal of headache. Buy a test kit for gold karat also. I have been practically given white gold, at silver prices. It is not my duty to inform sellers of their mistake, though I do if they appear in need.

Using the magnet, and another trick; sanding a thin layer, can expose plated items, by visual proof of different color, even white metals intended to look like silver. A little practice will be a huge benefit to you. Buying is where you make your money, so these hints are key to being consistently accurate in your estimate of value.

Then, if you have more questions, ask again here.

 

[METLMASHER]

Beyond those hints, I would wait for a professional refiner to give the best answer.

 

[dcapone2004]

I should clarify after masher's post that most of the metal in question is in the form of thin wire on spools. So it is very unlikely to be filled, etc. The jewelry itself, agree on all points about sanding, cutting, etch to determine what the true base metal may be.

Coming from a jeweler, my thoughts are that the solder is most likely a fairly high silver content solder to not affect any jewelry it may have been used on.

Some spools are labeled 6kt, and other wire is rolled in a ball that looks identical to the spool labeled 6kt. All these different hints lead me to believe there is some value here, the issue is finding the best process to test/refine.

 

[METLMASHER]

Coming from a jeweler, you will know that the value exceeds its scrap value considerably, if it is solder for jewelry. Testing it so you know for sure is diligent. Selling it once you do know, is wisdom.

 

[dcapone2004]

Is that true even though it is only 6 kt? I figured at 6kt there would not have been any worth without refining.

Also, without melting down and weighing before and after refining, I am not sure if it I will have a way to prove that it is 6kt gold solder as most test kits only test as low as 10kt.

I actually first took it to a jewelry store to see if they could test and the 4 I went to the area all used the same acid tests, so they couldn't verify it either to be 6kt.

 

[nickvc]

As stated before nitric is your friend here, for those who don't know your 6k is already to dissolve all but the gold if it is indeed a gold alloy!
The use of nitric for the suspected silver allows for a simple test by just adding table salt to the solution or adding a piece of copper, all details of testing is here on the forum you just have to look.
Ps I ran my own successful refinery for many years.

Edited for grammar.

 

[METLMASHER]

Did a bit of reading and 6k solder is used for sizing and repairs. It will match some, but not all, color applications, plumb gold solder is preferred for this reason, and the stamping act. The 6k is easy solder, but will lower overall gold content by weight.

I was sniping a fleabay k solder auction at $38.00 and in 25 seconds the bid went to $85.00. Break even for the known gold quantity was at $53.00, so listing it there is an option. Depends on how well you sell it, and if the crazy bidders get whiff of it 8)

 

[dcapone2004]

So, I made some shots out of what I thought to be the 6k gold solder and hit it with some nitric.

I ended up with a purple precipitate and a light blue solution. I am guessing I have silver in solution, however, what could the purple precipitate be? From reading these forums, it appears that it could be some type of gold/tin mix. Is there a way to recover the gold from this? Is there a process that I could use to prevent this from occurring again?

I am still considering the fleabag route, except I have some pause in going that way...

1. The solder is not stamped in any way, so I feel like it is going to be difficult to sell as solder without any type of verification stamp.
2. After fees and shipping, the premium is not that great and while the example auction would have netted an extra 30%, I feel like some will net extra and some may potential lose money after all fees over refining the metal. So at the end of the day, the net premium across the board will probably be closer to 10%-15% which may not be worth it to me for the extra time involved to create and manage all of the listings.