TORBERNITE (or cupro-uranite)  , a mineral which is one of the " uranium micas "; a hydrous uranium and copper phosphate, Cu(UO2)2(PO4)2+12H2O . Crystals are tetragonal and have the form of square plates, which are often very thin . There is a perfect micaceous cleavage parallel to the basal plane, and on this face the lustre is pearly . The bright grass-green colour is a characteristic feature of the mineral . The hardness is 22 and the specific gravity 3'5 . The radio-activity of the mineralis greater than that of some specimens of pitchblende . It was first observed in 1772 at Johanngeorgenstadt in Saxony, but the best examples are from Gunnislake near Calstock and Redruth in Cornwall . The name torbenite is after Torbern Bergman: chalcolite is a synonym . (L . J .