It is a pigment of inorganic and mineral origin, known to the ancient civilizations of the Egyptians, Greeks, Romans, and Byzantines. It is a basic copper carbonate obtained from ground malachite. It alters and blackens when heated and in the presence of alkalis, acids, and sulfides. It has excellent hiding power. It can be used in fresco, tempera, and oil painting. Not recommended for encaustic.
Refractive index: 1.87
Chemical formula: CuCO3 * Cu(OH)2
Mineral origin: Congo