Conichalcite

This specimen is Conichalcite from the Dome Rock Copper Mine, Boolcoomatta, South Australia, Australia, measuring 87 x 65 x 32 mm and weighing 297 g. It is drawn from the David Vince Collection. Conichalcite is a copper-calcium arsenate that typically forms as botryoidal or crusty apple-green to emerald-green aggregates in the oxidised zones of copper deposits, where circulating groundwater has carried arsenic and copper into contact with calcium-bearing host rock. It belongs to the Adelite-Descloizite group and forms a chemical series with Austinite, the calcium-zinc arsenate, so specimens from a single locality can show some variation in colour and composition along that range. Boolcoomatta, in the copper-bearing country of South Australia's Olary Domain, is a recognised Australian source for the species, with the Dome Rock workings among the historic small copper mines of the district. At 87 x 65 x 32 mm and 297 g, this is a substantial specimen for the species, giving good coverage of the characteristic green crust. Conichalcite is moderately hard and generally stable under normal display conditions, though as with most secondary copper arsenates it is best kept out of prolonged direct sunlight to preserve colour. The specimen's documented provenance is the David Vince Collection.