Molybdenite

Molybdenite
Euhedral molybdenite on quartz, Molly Hill mine, Quebec, Canada. The large crystal is 15 mm across
General
CategorySulfide mineral
Formula
(repeating unit)
Molybdenum disulfide (MoS2)
IMA symbolMol[1]
Strunz classification2.EA.30
Crystal systemCommon, 2H polytype: hexagonal
3R polytype: trigonal
Crystal class2H polytype: dihexagonal dipyramidal (6/mmm)
3R polytype: Ditrigonal pyramidal (3m)
Space group2H polytype: P63/mmc
3R polytype: R3m
Unit cell2H polytype: a = 3.16 Å,
c = 12.3 Å; Z = 2
3R polytype: a = 3.16 Å,
c = 18.33 Å; Z = 3
Identification
ColorBlack, lead-silvery gray
Crystal habitThin, platy hexagonal crystals terminated by pinacoidal faces, also as tapering six-sided pyramids that can be truncated by the pinacoids. Also massive, lamellar and in small grains in sulfide ore bodies
CleavagePerfect on [0001]
TenacityLamellae flexible, not elastic
Mohs scale hardness1–1.5
LusterMetallic
StreakBluish gray
DiaphaneityNearly opaque; translucent in thin flakes
Specific gravity4.73
PleochroismVery strong
FusibilityInfusible (decomposes at 1185 °C)
Other characteristicsIt has a greasy feel and leaves marks on fingers
References[2][3][4][5][6]

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.[3][4][7]

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Mineralienatlas
  3. ^ a b Handbook of Mineralogy
  4. ^ a b Mindat.org
  5. ^ Webmineral data for Molybdenite
  6. ^ Dana's Manual of Mineralogy ISBN 0-471-03288-3
  7. ^ Molybdenite 3R on Mindat