COVELLITE, a mineral species consisting of cupric sulphide, CuS, crystallizing in the hexagonal system. It is of less frequent occurrence in nature than chalcocite, the orthorhombic cuprous sulphide. Crystals 'are rare, the mineral being usually found as compact and earthy masses or as a blue coating on other copper sulphides. The dark indigo-blue colour is a characteristic feature, and the mineral was early known as indigo-copper (Ger. Kupfer indig). The name covellite is taken from N. Covelli, who in 5839 observed crystals of cupric sulphide encrusting Vesuvian lava, the mineral having been formed here by the interaction of hydrogen sulphide and cupric chloride, both of which are volatile volcanic products. Covellite is, however, more commonly found in copper bearing veins, where it has resulted by the alteration of other cop per sulphides, especially chalcopyrite. It is found in many copper mines. (L. J. S.)