Auricupride
Auricupride is a natural alloy that combines copper and gold. Its chemical formula is Cu3Au. The alloy crystallizes in the cubic crystal system in the L12 structure type and occurs as malleable grains or platey masses. It is an opaque yellow with a reddish tint. It has a hardness of 3.5 and a specific gravity of 11.5.<ref name=Handbook>http://www.handbookofmineralogy.org/pdfs/auricupride.pdf Handbook of Mineralogy</ref>
A variant called tetra-auricupride (CuAu) exists. Silver may be present resulting in the variety argentocuproauride (Template:Chem2).<ref name="Mindat">Template:Cite web</ref>
It was first described in 1950 for an occurrence in the Ural Mountains in Russia. It occurs as low temperature unmixing product in serpentinites and as reduction "halos" in redbed deposits. It is most often found in Chile, Argentina, Tasmania, Russia, Cyprus, Switzerland and South Africa.<ref name=Handbook/><ref name=Mindat/>