Melt Scrap Gold then Gravity Test

[daviec]

Hey Guys,

I regularly buy kilo+ lots of scrap jewelery and am getting tired of sorting through big bags weeding out all the plated and non gold rubbish. Recently bought a gravity testing gold machine and works quite well however does not work with hollow pieces.

I was wonder if i were to clean all jewelry ie remove stones etc etc then melt all into one big blob (probably in one of these electro furnaces) would i then get an accurate gravity reading when i test the blob at the end of it.. would it average out accurately with all the different karats combined inc some scrap that would be plated etc etc, have no experience in actually melting precious metals.

advice or opinions would be appreciated.

david

 

[goldsilverpro]

I regularly buy kilo+ lots of scrap jewelery and am getting tired of sorting through big bags weeding out all the plated and non gold rubbish. Recently bought a gravity testing gold machine and works quite well however does not work with hollow pieces.

I was wonder if i were to clean all jewelry ie remove stones etc etc then melt all into one big blob (probably in one of these electro furnaces) would i then get an accurate gravity reading when i test the blob at the end of it.. would it average out accurately with all the different karats combined inc some scrap that would be plated etc etc, have no experience in actually melting precious metals.

You could get an accurate reading of the specific gravity of the "blob", but this would not provide you with other than ballpark information concerning the gold content. The SG is a combination of the Au and the other metals. Karat golds are never consistent as far as the other metals are concerned. Different jewelry mfgrs. use different recipes to end up with the specific color that they prefer. For example, the SG of yellow 14K usually ranges from 12.8 to 13.5, depending on the ratios of Ag, Cu, and Zn that were used in the alloy. If I were to sell any ingot of this mixed gold, I would surely want more accuracy than what a SG measurement would give me.

In my book, there is a chapter on buying karat gold using SG measurements. However. this is for buying and not for selling. When buying, depending on the percentage you pay, you usually have from 20% to 50% flexibility. The errors will generally average out over the long haul. Selling is different. To keep the person that's buying from you honest and to know what the stuff is really worth, I would want to know the value within 0.1%. You can't get near that with SG measurements.

The best way to determine the average gold content of a mixed pile of karat gold is to first properly melt it all together and cast it in an ingot mold. This can either be pin sampled while molten or the cooled bar can be drilled. The samples are then fire assayed for the gold content. Were it me, I would still sort out all the plated material before melting everything together, unless it represented a very small percentage of the total weight.

I am curious as to why you're buying the gold plated pieces to start with. Maybe you should re-evaluate your testing and buying procedures.

 

[daviec]

Thanks for the quick reply GSP,

At the moment I'm buying large kilo + lots from jewelers and pawn shops at 90% of spot and working on an approx 5% spread so not much room for error.

In the last couple months Ive been accurate to within 1% on probably 25 kilos, problem is all these jewelers don't know what they are doing and always include a lot of crap (plated or non gold items, i mean its fine for them when buying at 30% of spot from the general public) that is no good in these bags which i end up giving back to them, but it does take me approx a day to go through a kilo bag, check it all out acid test what im not sure on, cut grind away at stuff i think is plated and gravity weigh what i think is clean..

I would love to refine with a refiner however always find that i end up loosing up to 7-10% after accounting for treatment sometimes more once accounting for fee's, treatment & retentions etc, there must be a way to maximize my return at the end, I'm guessing the guy i then on-sell to must be self refining...

I mean these guys sell too me because they always believe there refiners are ripping them off and the way i do it is honest and straight forward.

Ive read through a lot of the posts on here re refining however i work for a small shop we have an office and not enough space for me to experiment with the chemicals and fire needed to refine and pin sample etc safely in small environment.. i'm guessing the fumes from the chemicals are not good in small office space,

Was hoping if i melt all into a blob the sg would be accurate enough but i get your point re all the other alloys..

Is there a general guide on here as to what sort of weight after treatments and retentions should be expected from refiners, does it depend on purities of incoming weight etc,

thanks for the link to your guide as well i think ill grab a copy

David

 

[Rhodium]

This might be a good read. :arrow: http://www.scribd.com/doc/29932873/The-Pawnbrokers-Guide-to-Testing-Metals

 

[qst42know]

In the last couple months Ive been accurate to within 1% on probably 25 kilos, problem is all these jewelers don't know what they are doing and always include a lot of crap (plated or non gold items, i mean its fine for them when buying at 30% of spot from the general public) that is no good in these bags which i end up giving back to them, but it does take me approx a day to go through a kilo bag, check it all out acid test what im not sure on, cut grind away at stuff i think is plated and gravity weigh what i think is clean..

If I had to guess they know exactly what they are doing, hoping you will miss a few.

I know a gold and silver buyer here locally who gets back billed by his refiner for shortages. If they promise delivery of 100 oz set the price and deliver only 98 oz they have to pay for 2oz. at spot(+) price. He does get paid for overages but with no fixed rate. (The quantities are just an example.)

Perhaps you could charge them for the shortage to keep them more diligent in their own buying and testing.

I don't know if this will work in your situation but it's one way to shift some responsibility.

 

[4metals]

If you're working at a 5% margin, which by the way with witnessing can be increased, you're talking 100K a year for your compensation. For that kind of money a small propane melter and a small assay hood should be in your business plan. There are tried and true procedures you can follow to make your job easier, in this business the guy who gets lazy, gets burned.

 

[goldsilverpro]

If I had to guess they know exactly what they are doing, hoping you will miss a few

.
I agree!!

You should return all the non-karat gold stuff to them, no matter how long it takes to sort it (BTW, I can't believe it takes a day to sort a KG). Once you melt it, it has lost it's identity.

I would melt it, stir it well, pour it into a bar, drill it on each side half way through in a total of 5 holes, and have the drillings fire assayed. I don't assay any longer, mainly because I stupidly relied on support from the members of this forum and got absolutely none, but I would have assayed this for $25. Cheap! After assaying, I would send the bar to http://aragold.com/ . I have not dealt with them but have never heard of any problems with them. One of our very knowledgeable moderators has sent material to them and has always felt he always got a 100% free shake. They pay 98% on the gold content but do not pay for silver or PGMs. I would certainly try them. Even if you don't have the drillings assayed, it always helps to have a few holes in the bars to make the buyer think you have had it assayed.

 

[nickvc]

Good advice all round,testing and sorting seems to take to long to me but it depends on your experience i suppose. You could melt and assay individual parcels and supply copies to your sellers if they trust you,maybe explain the time you spend checking each parcel,depends where you are in the world if your in the UK i can give you details of where to have assays done for £10 a time usually done same day.The other alternative is buy an xrf gun which many bulk live scrap buyers use now to speed checking times up.

 

[daviec]

thanks for the thoughts and opinions, given me much to think about,