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Formula: MoS2
Sulphide
Oxidation states: Mo4+S2-2
Specific gravity: 4.7 to 4.8
Hardness: 1 - 1½
Streak: Dark grey
Colour: Lead-grey
Solubility: Moderately soluble in sulphuric and nitric acid
Environments:
Plutonic igneous environments
Pegmatites
Carbonatites
Metamorphic environments
Hydrothermal environments
Molybdenite forms as an accessory mineral in some igneous rocks and in pegmatites. It is found in
contact metamorphic deposits, and it is important in disseminated deposits of
the porphyry (with coarse crystals or mineral grains phenocrysts in a finer groundmass) type. It is common as a
primary mineral in
hypothermal (high temperature) hydrothermal veins.
Molybdenite may be found in some
granites, including
aplite
In contact metamorphic deposits it is associated with lime silicates,
scheelite and
chalcopyrite.
In hypothermal (high temperature) hydrothermal veins it is associated with
cassiterite,
scheelite,
hübnerite-ferberite
and
fluorite.
Localities
At Mount Moliagul, Moliagul, Central Goldfields Shire, Victoria, Australia, molybdenite occurs throughout the
aplite dykes and quartz veins in
the granodiorite, forming crystals up to 2 cm, sometimes associated
with muscovite
(AJM 21.1.43).
At the Faraday mine, Faraday Township, Hastings county, Ontario, Canada, molybdenite crystals to
8 cm across occur in small calcite veinlets
(R&M 94.5.414).
At the Pioneer quarry, Kwun Tong District, Kowloon, Hong Kong, China, the contact between
granite and tuff is very sharp,
and many veins and stringers of aplite and
pegmatite from the batholith invade the country rock. The
granite near the contact contains crystals of
fluorite, pyrite,
molybdenite and quartz, and
calcite-filled vugs. Calcite also
occurs along joint planes
(Geological Society of Hong Kong Newsletter 1.7.6).
At Devil's Peak, Sai Kung District, New Territories, Hong Kong, China, the mineralisation occurred in
quartz veins in the contact zone between a
granite intrusion and acid volcanic rocks. The mine is now closed,
and inaccessible for collecting.
Molybdenite occurred in the quartz veins with
beryl, wolframite,
chalcopyrite, pyrite and
arsenopyrite
(Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council)
The Needle Hill Mine, Needle Hill, Sha Tin District, New Territories, Hong Kong, China, is a tungsten mine, abandoned
in 1967. The principal ore is wolframite, and the principal gangue mineral is
quartz. Molybdenum also occurs. The
mineralisation consists of a series of parallel fissure veins that cut through
granite. Wolframite and
quartz are the main minerals, but galena,
sphalerite, pyrite,
molybdenite and fluorite have also
been found here
(Geological Society of Hong Kong Newsletter 9.3.29-40).
The quartz-wolframite veins are of
high-temperature hydrothermal formation,
and grade into wolframite-bearing
pegmatites.
Molybdenite occurs in the quartz veins, in some cases in greater
quantities than wolframite
(Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council)
The Lin Fa Shan deposit, Tsuen Wan District, New Territories, Hong Kong, China, is located in a remote area of the Tai Mo Shan
Country Park, on a steep west facing slope of Lin Fa Shan, just above the abandoned village of Sheung Tong. The
surrounding hillsides are covered with shallow excavations, representing past searches for
wolframite, the natural ore of
tungsten. The abandoned workings are extremely dangerous with unsupported tunnels, open shafts and no maintenance since
their closures in 1957; the workings should not be entered
(http://industrialhistoryhk.org/lin-shan).
Pyrite occurs here in
wolframite-molybdenite-quartz
veins
(Hong Kong Minerals (1991). Peng, C J. Hong Kong Urban Council).
At the Sherlov mountain, Transbaikalia, Russia, molybdenite occurs with
ferrimolybdite
(FM 53392).
At Croft Quarry, Croft, Blaby, Leicestershire, England, UK, molybdenite occurs associated with
analcime, calcite,
laumontite and prehnite in a thin
granite pegmatite vein running through tonalite.
The molybdenite forms small foliated masses and nests of very thin plates, up to 3 mm in diameter. The plates are often strongly
malformed and curved round quartz and feldspar crystals
(JRS 20.21).
At the Main quarry, Mountsorrel, Leicestershire, England, UK, molybdenite occurs with
allanite and titanite on
granodiorite
(RES p192).
At the Childs-Adwinkle Mine, Copper Creek, Bunker Hill District, Pinal county, Arizona, USA, molybdenite occurs as crystals over 2 cm.
It typically occurs in quartz-rich veins with
chalcopyrite and pyrite
(R&M 96.2.155).
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