Chalcopyrite is a copper iron sulphide (CuFeS2), a mineral with a gold-like lustre that runs away into faint, yellow, green, and blue iridescent colours. In this sample it occurs as a coating on a substrate of magnetite. It is closely related to and easily confused with pyrite (FeS20) and both minerals are popularly referred to as fool?™s gold. The crystal habitat is tetragonal, but crystals are usually poorly developed, and occurrences of the mineral usually have the nature of an irregular, fragmented mass or crust, as seen in this sample. Actual width is 110 mm.