Molybdenite

molybdenite

allanite

titanite

ferrimolybdite

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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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