Forming pseudotetrahedral crystals, often with striated faces and commonly twinned, chalco pyrite can also occur in compact, massive, reniform, or botryoidal habits. It is brassy yellow in color, often with an iridescent tarnish. There is a greenish-black streak. The mineral has a metallic luster and is opaque.
FORMATION One of the most important ores of copper, chalcopyrite forms in sulfide ore deposits. These are often hydrothermal veins, where it may occur with pyrrhotite, quartz, calcite, pyrite, sphalerite, and galena. It is also present where copper deposits have been altered.
TESTS It is soluble in nitric acid and colors a flame green.
Group: SULFIDES
Composition: CuFeS₂
Hardness: 3½–4
SG: 4.35
Cleavage: Poor
Fracture: Uneven to conchoidal
