Mineralogy classified into density (often given as specific gravity); measures of mechanical cohesion (hardness, tenacity, cleavage, fracture, parting); macroscopic visual properties (luster, color, streak, luminescence, diaphaneity); magnetic and electric properties; radioactivity and solubility in hydrogen chloride (). "Hardness" is determined by comparison with other minerals. In the Mohs scale, a standard set of minerals are numbered in order of increasing hardness from 1 (talc) to 10 (diamond). A harder mineral will scratch a softer, so an unknown mineral can be placed in this scale by which minerals it scratches and which scratch it. A few minerals such as calcite and kyanite
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