Molybdenite is a mineral of molybdenum disulfide, MoS2. Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet of molybdenum atoms sandwiched between sheets of sulfur atoms. The Mo-S bonds are strong, but the interaction between the sulfur atoms at the top and bottom of separate sandwich-like tri-layers is weak, resulting in easy slippage as well as cleavage planes.
Molybdenite crystallizes in the hexagonal crystal system as the common polytype 2H and also in the trigonal system as the 3R polytype.
Euhedral molybdenite on quartz, Molly Hill mine, Quebec, Canada. The large crystal is 15 mm across
A less pure sample of molybdenite mineral
Molybdenite under normal and polarized light
Molybdenum disulfide is an inorganic compound composed of molybdenum and sulfur. Its chemical formula is MoS2.
Molybdenum disulfide
Molybdenite
Electron microscopy of antisites (a, Mo substitutes for S) and vacancies (b, missing S atoms) in a monolayer of molybdenum disulfide. Scale bar: 1 nm.
A tube of commercial graphite powder lubricant with molybdenum disulfide additive (called "molybdenum")