molybdenite (məlĭbˈdənĪt, mō–) [key], 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.