I am interested in a source for 22K gold, I found good information of the krugerrand about hardness, melting point etc, but have found nothing in the American eagle. The composition is 91.7% gold, 3% silver amd 5.3% copper. What would it’s melting point and hardness be? Has anyone used American eagles as a source for 22K gold? What about Krugerrands? If so how was the workability and colour of the two coins?
I have zero experience with 22 kt gold, but I found this reference in a patent discussion which gives Brinell hardnesses for several alloys, two of which are close to the American Eagle alloy which you reference. Evidently all of these are pretty soft in their annealed state and they all increase in hardness with cold working (quoted as a percent reduction in the table provided).
Here’s the link: https://patents.google.com/patent/WO2002018664A1/en
These coins are currently available for about 1% over spot, which you may know, but I didn’t.
Whether there’s a magic alloy that can be heat treated to a greater hardness or not, etc., etc., I don’t know, but I’d certainly consult some of the refiners if this were an issue. IDK how you’d be sure of enough work hardening all over your piece to be sure it is protected from wear…HTH, royjohn
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Very helpful, thanks 