Epidote is a calcium aluminium iron sorosilicate mineral, with the formula Ca2Al2(Fe3+;Al)(SiO4)(Si2O7)O(OH). It is a rock forming mineral of secondary origin, occurring in marble and schistose rocks of metamorphic origin. It may also occur as a product of the alteration of the usual minerals found in igneous rocks, for instance, micas, amphiboles, feldspars, pyroxenes. The randomly orientated crystals in this specimen are prismatic, and are very dark green, almost black in colour. It was collected from Mount Painter, in South Australia, by the club co-founder Jim Nicholls, while working at Woomera.