Friedrich Mohs harder. This became the basis of the hardness scale developed by Mohs. The hardest mineral, diamond was given a value of 10 and softer minerals such as talc were given the very low value of 1 (unity). Other minerals were given intermediate values, depending on their ability to scratch another mineral in the scale. Thus gypsum was given the value 2 because it will scratch talc crystals, and calcite the value 3 because it will scratch gypsum. Minerals are also now classified by chemical characteristics, but the physical properties are still useful in field examination. In 1812, Mohs became a
Chalcocite Chalcocite Chalcocite (), copper(I) sulfide (CuS), is an important copper ore mineral. It is opaque and dark-gray to black with a metallic luster. It has a hardness of - 3 on the Mohs scale. It is a sulfide with an orthorhombic crystal system. The term chalcocite comes from the alteration of the obsolete name "chalcosine", from the Greek "khalkos", meaning copper. It is also known as redruthite, vitreous copper and copper-glance. Chalcocite is sometimes found as a primary vein mineral in hydrothermal veins. However, most chalcocite occurs in the supergene enriched environment below the oxidation zone of copper deposits as