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Molybdenite
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Molybdenite is named from the Greek molybdos for lead.

Discovered in 1807.   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

MoS₂

Molybdenum Sulfide

Molecular Weight:

160.07 gm

Composition: 

Classification

Mineral Classification:

Sulfides

Strunz 8th Ed. ID:

2/D.25-10

Nickel-Strunz 10th Ed. ID:

2.EA.30

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
E : Metal Sulfides, M: S <= 1:2
A : M:S = 1:2 - With Cu, Ag, Au

Related to:

Molybdenum Group. Dimorphous with Jordisite. Two polytypes are known: Molybdenite-2H (very common) and Molybdenite-3R (rare).

Varieties:

Femolite, Rhenian Molybdenite

Synonyms:

Castaingite-(Cu), Molybdic Ochre, Muchuanite - a mixture of Molybdenite and Jordisite

Crystal Data

Crystallography:

Hexagonal - Dihexagonal Dipyramidal

Crystal Habit:

Crystals are commonly tabular, barrel shaped; also as slightly tapered prisms; face development poor; up to 15 cm across. Commonly shows trigonal markings on {0001} parallel to the trace of {1011}. Foliated, massive, or in scales.

Twinning:

None

Physical Properties

Cleavage:

[0001] Perfect

Fracture:

Sectile

Tenacity:

Lamellae flexible, not elastic

Moh's Hardness:

1.0

Density:

4.62 - 4.73 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Black, lead Gray, Gray, Silvery Black with a Bluish cast

Transparency:

Opaque to nearly Opaque; translucent in thin flakes; transparent in infrared light

Luster:

Metallic

Refractive Index:

R1–R2: (400) 21.0–55.0, (420) 22.2–54.8, (440) 23.4–54.6, (460) 24.1–53.8, (480) 23.8–52.3, (500) 22.7–49.7, (520) 21.9–47.1, (540) 21.3–45.5, (560) 20.9–44.4, (580) 20.6–44.0, (600) 20.4–44.6, (620) 20.2–45.3, (640) 20.0–45.7, (660) 20.0–45.6, (680) 19.9–45.4, (700) 19.7–44.2

Birefringence:

0.0140

Pleochroism:

Very Strong

Anisotrophism:

Very Strong; Color in reflected light: gray, very pale yellow to deep reddish brown in transmitted light.

Occurances

Geological Setting:

In high-temperature hydrothermal veins. In disseminated deposits of the porphyry type, both with and without associated major copper mineralization. Also in contact metamorphic deposits in limestone with calcium silicate minerals as well as in pegmatites, granites, and aplites. Rarely in meteorites.

Common Associations:

Chalcopyrite, other copper sulfides

Type Locality:

Common world wide occurrences

Year Discovered:

1807

View mineral photos:

Molybdenite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Molybdenite is a very soft metallic mineral that is rarely available as a faceted gem. Due to its color and softness, it can easily be confused with Graphite. Graphite is a slightly darker silvery black and Molybdenite is usually silvery black with a bluish cast. Molybdenite however has a greater density of 4.62 - 4.73 than Graphite's 2.09 - 2.23. Both are soft enough to leave black on your fingers when handling. Molybdenite is slight softer at 1.0 on the Moh's scale, while Graphite is about 1.0 - 2.0. Because of its extreme softness and metallic luster, Molybdenite has a greasy feel.

Molybdenite is of widespread occurrence; the most abundant molybdenum mineral. Fine crystals occur, in the USA, at the Crown Point mine, Lake Chelan, Chelan County, Washington; and at the Frankford quarry, Philadelphia, Pennsylvania. In Canada, in the Temiskaming district, and in Aldfield Township, Quebec. In Norway, from Raade, near Moss, and at Vennesla, near Arendal. In Russia, in the Adun-Chilon Mountains, south of Nerchinsk, Transbaikal; at Miass, Ilmen Mountains, Southern Ural Mountains; and in the Slundyanogorsk deposit, Central Ural Mountains. In Germany, at Altenberg, Saxony. In Morocco, at Azegour, 80 km southwest of Marrakesh. From Kingsgate and Deepwater, New South Wales, Australia. At the Hirase mine, Gifu Prefecture, Japan. In the Wolak mine, Danyang, Chungchong Province, South Korea. The 3R polytype occurs in the Con mine, Yellowknife, Yukon Territory; and at Mont Saint-Hilaire, Quebec, Canada. From the Yamate mine, Okayama Prefecture, Japan.
 

  
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