Most common copper mineral, CuFeS₂; sp. gr. 4.1–4.3; hardness 3.5–4.0; tetragonal; brass-yellow, often with an iridescent tarnish; greenish-black streak; metallic lustre; sometimes massive, crystals usually tetrahedra; cleavage imperfect {011}; primary mineral found in igneous rocks and hydrothermal veins, in association with pyrite, pyrrhotite, cassiterite, sphalerite, galena, calcite, and quartz, an important mineral in porphyry copper deposits, and also occurs in quartz diorite, and in pegmatites, crystalline schists, porphyry copper deposits, syngenetic copper ores and skarns, and contact metamorphic zones. It is deeper in colour than pyrite, more brittle and harder than gold, is soluble in nitric acid, and its alteration products are secondary copper minerals. It is a major ore mineral for copper.