FMF - Friends of Minerals Forum, discussion and message board

[Roger Warin]

Hi,
Here is a crystallized gold, in fact a Cuprian Gold from Mt. Karabasch (Urals) (Claude Hootelé Collection). AuCu.
This gold can tarnish because it is susceptible to weathering in damp air. "Cuprian Gold is known from Borneo (containing over 5 percent copper) and from Mt. Karabasch in the Urals (over 20 percent copper); the Urals material, reported in 1914, is near the composition of the recently described tetra-auricupride (ideally containing 24.4 percent copper)."
From Mineralogical Record Vol. 13, p. 290.
Roger.

[alfredo]

Probably would be a good idea to have this piece microprobed. Looks a bit too yellow to be AuCu.
Impressive crystal anyway.