Mineral Variety

individual minerals united by their most important characteristics into a single mineral species but distinguished by the existence of elements in their chemical (elemental) composition that are capable of isomorphically replacing one species-forming element or group of elements. For example, molybdoscheelite Ca[(W, Mo)O₄] is a variety of scheelite Ca[Wo₄]. Mineral varieties are sometimes identified by other, purely external characteristics, such as color, diaphaneity, and shape. Varieties of quartz (rock crystal, amethyst, morion, chalcedony), hematite (iron glance, red ocher), and corundum (sapphire, ruby) are identified by such external characteristics.