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molybdenite(məlĭb`dənīt, mō–), a mineral, molybdenum disulfide, MoS2, blue-gray in color, with a metallic luster and greasy feel. It occurs in crystals of the hexagonal system but more commonly in scales, grains, or foliated or massive form. It has an excellent basal cleavage and the laminae are flexible. It is found in granites, syenites, gneisses, and crystalline limestones. Molybdenite is an important ore of molybdenum. The major sources are quartz veinlets in granite at Climax, Colo., and copper mines in Utah, New Mexico, and Arizona. Minor amounts are recovered in Mexico, Chile, Canada, and Norway.
(molybdenum glance), a mineral of the sulfide class, with chemical composition MoS2, containing 60 percent Mo, 40 percent S, and a negligible quantity of Re (up to 0.33 percent). Molybdenite crystallizes in a hexagonal system to form crystal structures in which molybdenum atoms surrounded by six sulfur atoms are located in the center of trigonal prisms, whose apices are occupied by sulfur atoms. The trigonal prisms form layers that contain strong metal-covalent interatomic bonds. Weak residual van der Waals bonds are observed between layers. This distinct lamellar structure determines the habit of molybdenite crystals, which varies from tabular to squamous, and their perfect cleavage, . Molybdenite occurs as squamous or foliated aggregates and is steel-gray, with a bright metallic luster. Mineralogical hardness, 1.0–1.5; density, 4,620–4,800 kg/m3.
Molybdenite occurs in greisen deposits and, less frequently, in pegmatite deposits, where it exists in association with wolframite, topaz, cassiterite, fluorite, chalcopyrite, and pyrite. Large molybdenite deposits are located in contact-metasomatic garnetpyroxene skarns, as well as in hypothermal and mesothermal quartz-molybdenite ore veins. Molybdenite deposits are found in the Caucasus, Transbaikalia, Middle Asia, the USA (Climax, Colorado), Mexico, and Norway. Molybdenite is the most important constituent of molybdenum ores.