Crystal structure and XANES investigation of petzite, Ag3AuTe2.

Petzite, Ag3AuTe2, crystallizes in the space group I4132, which is a Sohncke type of space group where chiral crystal structures can occur. The structure refinement of petzite reported long ago [Frueh (1959). Am. Mineral. 44, 693-701] did not provide any information about the absolute structure. A new single-crystal X-ray diffraction refinement has now been performed on a sample from Lake View Mine, Golden Mile, Kalgoorlie, Australia, which has resulted in a reliable absolute structure [a Flack parameter of 0.05 (3)], although this corresponds to the opposite enantiomorph reported previously. The minimum Te-Te distance is 3.767 (3) Å, slightly shorter than the van der Waals bonding distance, which suggests a weak interaction between the two chalcogens. XANES spectra near the Au and Te LIII edges suggest that the chemical-bonding character of Au in petzite is more metallic than in other gold minerals.