Chalcopyrite (Copper Iron sulfide) is a Copper ore and is the leading source of Copper worldwide. It has a brassy to golden yellow color with a metallic luster (often confused with Pyrite). It is a very appealing mineral, with abundant quality specimens available. It is associated with numerous aesthetic minerals, including Quartz, Calcite, Pyrite, Fluorite, Siderite and Barite. Note: Popular among some collectors and tourists, and often incorrectly labeled as a variety of Bornite, most “Peacock Ore” is, in fact, Chalcopyrite treated with acid to produce an iridescent tarnish. Though it can be naturally iridescent, strong and unnatural colors such as bright blues and purples are a clear sign that an acid bath was involved.
The crystal system for Chalcopyrite is tetragonal, forming slightly asymmetrical tetrahedral crystals (a disphenoid). Other forms include grainy, botryoidal, reniform, striated in different directions (appearance of offset layering), twinned and massive.
Chalcopyrite and quality specimens are found in abundance. Notable locations include China, England, Germany, Mexico, Peru, Romania and the USA (Pennsylvania, Tri-state mining district of Kansas, Oklahoma and Missouri).