Wittichenite from the Cattle Grid Pit, Mount Gunson Mine, South Australia

In 1981, large, attractive wittichenite crystals found at the Cattle Grid Pit in South Australia were mistaken for chalcocite. Then in 2008, they were correctly identified by the Smithsonian Institution. Electron microprobe analysis of this species shows Cu, Bi, and S (weight percentages of 38.67%, 41.70%, and 19.90%, respectively).

The Cattle Grid wittichenite is brittle, with strongly conchoidal fractures and a relatively low hardness. The colors vary from highly lustrous silvery white to bronze to a deep purple-black. The crystals are predominantly tabular-prismatic in habit, but some show myriad crystal faces and deeply striated prisms. The Miller indices for these crystal forms, and their intricate and complicated crystal morphology, are discussed in depth.

The article contains 16 large photos of wittichenite, some crystals weighing more than 75 grams, as well as the mine site and the copper localization stratigraphy. The number of wittichenite crystals larger than 2 cm in maximum dimension is estimated to be about 30, and these are held in only three collections (two institutional and one private). Unfortunately, the entire production of copper sulfide concentrate from the Cattle Grid Pit is now owned by a private smelter, where the bismuth-containing wittichenite is considered an undesirable impurity.