Chalcocite with Chalcopyrite, Tincroft Mine, Illogan, Cornwall, England
Steel coloured crystals of chalcocite covering chalcopyrite. This botryoidal variety of chalcopyrite is known as blister copper. The specimen was drawn for Specimens of British Minerals, Selected from the Cabinet of Philip Rashleigh (1797, Volume 1, Plate 9, Figure 4) which states 'Is yellow mammillary copper ore, covered with a thin coat of a bluish-green colour, with crystals of steel-coloured copper ore, composed of prisms having six sides, and truncated ends, formed upon the mammillary copper ore. d One of the steel-coloured crystals magnified. From Tincroft'. Chalcocite is a secondary mineral occurring in or near the oxidised zone of copper sulfide deposits. Rashleigh Collection.
© RIC, photographer A.G. Tindle