Molybdenite
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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... Wikipedia
Streak: Bluish gray
Density: 4.6-5.1
Cleavage: Perfect on
Color: Black, lead-silvery gray
Crystal class: 2H polytype: dihexagonal dipyramidal (6/mmm); 3R polytype: Ditrigonal pyramidal (3m)
Crystal system: Common, 2H polytype: hexagonal; 3R polytype: trigonal
Diaphaneity: Nearly opaque; translucent in thin flakes