COP PER-PYRITES. 115 of copper has a deep-yellow colour, approaching to gold- yellow ; the poorer varieties approach to greyish brass- yellow, and steel-grey. It is usually tarnished, either with variegated colours, as pavonine, columbine, and sometimes tempered-steel coloured, or with simple colours, as blue and black. The tarnished colours occur sometimes on the mineral in the bosom of the earth, sometimes by the exposition of the recent fracture to the action of the air. It occurs massive, disseminated, and in membranes; also dendritic, reniform, botryoidal, stalactitic, specular, amorphous ; and crystallised as follows : 1. Tetrahedron. a. Perfect *. b. Truncated on the angles f. c. Truncated on the edges j. d. In which each plane is divided into three com partments ||. e. The angles acuminated with three planes, which are set on the lateral planes. When the angles on the base are slightly truncated, but that of the summit deeply truncated, there is formed a 2. Six-sided table, in which the terminal planes are set alternately oblique and straight on the late ral planes. 3. Octahedron. a. Perfect. b. Truncated on the edges, thus forming a figure II 2 intermediate * Cuivre pyriteux primitif, llauy. ■f Cuivre pyriteux epointe, Hauy. X Cuivre pyriteux cubo-tetraedrc, Hauy. 11 Cuivre pyriteux dodccacdrc, Hauy.