Yields on carat scrap?

[turtlesteve]

Forum experts,

When I test karat scrap I often get pieces slightly under karat, but can't tell by how much. For those of you that refine karat scrap, or send it off for refining, what percent yield do you get on average, as in (grams gold recovered / grams predicted from karat markings)*100%? This would be assuming all filled/plated material and stones are removed.

I have noted around 97% - as in, 9.7K for marked 10K, or 13.6K for marked 14K. However this was a small sample size so I want to know if this is typical.

Steve

 

[turtlesteve]

Let me clarify: I want to know the average yield on pieces that acid test at nominally the marked Karat value - as pieces way under karat could be identified easily via acid testing.

Steve

 

[cyberdan]

I have noted around 97% - as in, 9.7K for marked 10K, or 13.6K for marked 14K

You are right on. By law it is OK for a jewelry maker to be up to 1/2 K low if he stamps his work and if he use gold solder he can be uo to 1 K low. I very rarely see anything test as marked. I have a electronic tester that I feel is very accurate to half a K.

also a lot of makers are more than 1/2K low. I test first then pay based on the test.

 

[Fournines]

I have noted around 97% - as in, 9.7K for marked 10K, or 13.6K for marked 14K

You are right on. By law it is OK for a jewelry maker to be up to 1/2 K low if he stamps his work and if he use gold solder he can be uo to 1 K low. I very rarely see anything test as marked. I have a electronic tester that I feel is very accurate to half a K.

also a lot of makers are more than 1/2K low. I test first then pay based on the test.

What is 'legal' and what is actually done are two different things.

I've posted this before, but here is what is required of jewelry manufacturers: http://www.jvclegal.org/JVC_guide.pdf

When I get back to the office on Monday, I'll post the results of several melts from a customer of mine. We specifically did 3 separate melts: One was only 10k scrap, one was 14k, the last was 18k.

 

[goldsilverpro]

Fournines,

I look forward to those numbers

 

[Barren Realms 007]

I have noted around 97% - as in, 9.7K for marked 10K, or 13.6K for marked 14K

You are right on. By law it is OK for a jewelry maker to be up to 1/2 K low if he stamps his work and if he use gold solder he can be uo to 1 K low. I very rarely see anything test as marked. I have a electronic tester that I feel is very accurate to half a K.

also a lot of makers are more than 1/2K low. I test first then pay based on the test.

What is 'legal' and what is actually done are two different things.

I've posted this before, but here is what is required of jewelry manufacturers: http://www.jvclegal.org/JVC_guide.pdf

When I get back to the office on Monday, I'll post the results of several melts from a customer of mine. We specifically did 3 separate melts: One was only 10k scrap, one was 14k, the last was 18k.

Are you going to do a complete assay where you can post what percentage of other PM's are in the different karat mixes?

Thanks

 

[turtlesteve]

I'd also be interested in the complete assay. I suspect most of the modern 10K and 14K alloys have fairly low silver content, but I'd be interested in seeing actual numbers.

Steve

 

[Fournines]

As promised, here are some figures from a recent melt for a customer. The three different karats were separated by the customer and melted separately. We did fire assays for Gold and Silver, but I had our lab put the reserve samples through our XRF today to get approximate reads on the other elements. I've noted those with an **

10k
Before melt: 9.37
After melt: 9.25
Au: 40.70%
Ag: 12.35%
Cu: 40.26%**
Zn: 5.85%**
Ni: 0.201%**

14k
Before melt: 90.89
After melt: 89.55
Au: 56.96%
Ag: 8.77%
Cu: 28.56%**
Zn: 5.05%**
Ni: 0.473%**

18k
Before melt: 35.14
After melt: 34.87
Au: 73.15%
Ag: 11.59%
Cu: 13.45%**
Zn: 0.985%**
Ni: 0.592%**

This particular customer runs a gold buying store and is not a manufacturer. What was melted probably spans many years (if not decades), and is not necessarily produced using modern alloys.

 

[EDI Refining]

Great info Matt

Curious what did your XRF read for the Au,Ag content? Like to know, how close to the fire assay it was. What XRF are you guys using at So Accurate?

 

[goldsilverpro]

Excellent, fournines! Thanks a lot. I'm surprised to see the silver that high.

 

[turtlesteve]

Thanks Fournines, this is exactly the kind of information I'm looking for. Seems like the 97% I'm seeing is pretty close to target.

Steve

 

[Fournines]

We're using a Spectro Midex XRF.

The readings are pretty close to the fire assay. It's great to be able to check things out before melting to ensure there aren't any deleterious elements like cadmium or beryllium.

 

[goldenchild]

With the information Fournines has provided us and the fact that these readings were from material that spans many years, I think its safe to conclude that karated jewelry is almost never plumb.

 

[Harold_V]

With the information Fournines has provided us and the fact that these readings were from material that spans many years, I think its safe to conclude that karated jewelry is almost never plumb.

Rarely did I encounter plumb gold. Some of my experiences came in running literally pounds of a given type, such as class rings. In my experience, they bordered on being legal (just inside 9 K, to be clear), nothing more.

I commented previously that one of my customers proudly proclaimed to me that he always under-karated his gold. Said as if it was a badge of honor to be a crook. Mind you, this guy fancied himself a great designer and was trying to build his reputation.

If you do the math on gold alloying, it's easy to see why it is commonly under-karated. In order for it to make sense, you must understand that gold is alloyed by weight, not volume. By replacing gold with a specific gravity of 19.3 with copper and silver, average s.g. of about 10, it's clear that you can stretch the volume by near 10%. That's quite an incentive for a guy with low or no moral values, and finds it more important to gain unearned money than to present one's self to the world honorably.

Harold

 

[nickvc]

For a change I consider myself lucky to be UK based. The assay rules here are very strict and even slight failures to meet with the standard will or can result in destruction of the items. It's not impossible to buy below standard items but those that aim to cheat have to be creative ,silver wire rhodium plated instead of white gold .filling items with silver solder or sand to increase weight etc.
The only scrap I'll usually encounter below assay comes from abroad and doesn't have a full British hallmark but caution is always required as things do get missed.

 

[Harold_V]

I recall reading, early on in my refining experiences, that in years gone by, the penalty in the UK for mismarking precious metals was death. Likely a long time ago, but it suggests that the Brits take their hallmarks and precious metal content very seriously (as it should be).

Harold

 

[nickvc]

I recall reading, early on in my refining experiences, that in years gone by, the penalty in the UK for mismarking precious metals was death. Likely a long time ago, but it suggests that the Brits take their hallmarks and precious metal content very seriously (as it should be).

Harold

Harold I'm sure I've told this story before, we had a phone call from the Assay office to complain that the gold casting grain we had supplied one of our large customers was only reaching .375 Au ie 9 ct ,we always aimed to hit .376 Au ,but we didn't do the castings so someone had thrown some base into the mix! The margin for error here in the UK is slight! Most items marked 9 ct will be above the required assay it's easier and less complicated to be sure than not.

 

[Harold_V]

Harold I'm sure I've told this story before, we had a phone call from the Assay office to complain that the gold casting grain we had supplied one of our large customers was only reaching .375 Au ie 9 ct ,we always aimed to hit .376 Au ,but we didn't do the castings so someone had thrown some base into the mix!

I don't recall hearing that before, but then I often forget where I live! :lol:
I can see the problem-----once you have delivered the goods, no matter how well you've done your job, you are still at the mercy of the next guy. I expect that none of us are exempt from others that have no problem in cheating their fellow man. Even in jolly old England, it appears! 8)

Harold

 

[nickvc]

I must admit that I'm still a bit dubious of xrf results especially on low grade material but have seen reasonable results for carated products but would only fully trust a proper assay but that could just be my age :lol: