molybdénite

Molybdenite (MoS2) is a sulfide mineral and the principal ore of molybdenum. It occurs in igneous and metamorphic rocks as well as in hydrothermal veins, and is widely mined for its metal content. The mineral typically forms as thin, flexible, silver-gray flakes with a greasy or metallic luster.

Chemically, molybdenite has the formula MoS2 and belongs to the hexagonal crystal system. Its structure consists of layers of molybdenum atoms sandwiched between two planes of sulfur atoms; the layers are bonded strongly within but only weakly to each other, producing perfect basal cleavage and allowing easy exfoliation into sheets.

Physical properties include a lead gray to bluish gray color, a pale gray streak, hardness of about 1 to 2 on the Mohs scale, and a specific gravity around 4.7. It forms tabular or foliate crystals and typically exhibits a metallic to pearly luster and is opaque. Its habit and cleavage are among the characteristic features used to identify it in hand specimens.

Occurrence and formation: molybdenite forms from hydrothermal fluids in porphyry copper deposits and in metamorphosed rocks, often in greisen and skarn environments. It is commonly associated with quartz, pyrite, calcite, sphalerite, and magnetite, and has a worldwide distribution with several major producing regions.

Economic and industrial significance: molybdenite is the principal ore mineral for molybdenum, which is primarily used as an alloying element to improve strength and high-temperature performance in steel and other alloys. The mineral can be roasted to produce molybdenum oxide, which is refined to metal. Its layered structure also gives molybdenite applications as a solid lubricant in various industrial settings.