Molybdenite has physical properties that often cause it to be confused with graphite. Both of these minerals are gray to silver in color, have a very low hardness, and occur in hexagonal crystals or foliated masses. Both minerals have a layered atomic structure with planes of extreme weakness. This gives them a slippery feel and makes them valuable as a solid lubricant.

Molybdenite has a higher specific gravity than graphite (molybdenite=4.7, graphite=2.23). Molybdenite usually has a slightly bluish-gray color and a slightly bluish-gray streak, while graphite’s color and streak are gray to black. Molybdenite usually has a higher luster than graphite. Experienced observers can often use these subtle differences in color, streak and luster to separate graphite from molybdenite. A variety of laboratory methods can also be used to identify molybdenite.