Molybdenite

Molybdenite (known by the mineral symbol Mol)[3] is a mineral form of molybdenum disulfide. It is similar to the texture of graphite. It sometimes has a slippery effect because of its structure, which is made of sheets of molybdenum and sulfur. It usually has a hexagonal shape, or has a trigonal shape.[2]

Molybdenite
Molybdenite ore on a quartz crystal.
General
Category	Mineral
Formula (repeating unit)	Molybdenum disulfide (MoS2)
Identification
Color	Black, Gray
Crystal habit	Thin, Hexagonal or Trigonal
Mohs scale hardness	1–1.5
Luster	Metallic
Streak	Bluish gray
Diaphaneity	Nearly non-transparent; transparent in thin parts
Pleochroism	Very strong
Other characteristics	It has a slippery feel and leaves marks on fingers
References	[1][2][3][4][5]

It occurs usually with minerals such as quartz or pyrite, and can be found in deposits across mines in the western US, notably New Mexico, Colorado, Utah, and Arizona. It can also be found in Mexico. Sometimes, Rhenium can be found in this mineral. It is very similar to graphite that it can be almost impossible in tell them apart.