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Formula: MoO3
Simple oxide of molybdenum
Specific gravity: 4.5
Hardness: 3 to 4
Streak: White
Colour: Colourless, light greenish yellow, light brown, also pale blue
Luminescence: Not fluorescent in UV
Environments
Hydrothermal environments Rare
Fumeroles
Molybdite is commonly found in fumerolitic conditions such as mine dump fires or volcanic fumeroles. It is
sometimes found as secondary alterations of molydenum-bearing ores.
Occurrences of hydrothermal origin are scarce. Molybdenite is a common
associate
(Mindat).
Localities
At the type locality, Quartz vein outcrops, Knöttel area, Krupka, Teplice District, Ústí nad Labem Region, Czech
Republic, molybdite was found in a quartz vein with
molybdenite, near the contact with fine-grained
topaz-quartz
greisen. It occurs in the coarse-grained
quartz in the cavities formed after total or partial "leaching" of
molybdenite, or in their close vicinity. A tabular crystal of
molybdenite altered on the surface into molybdite also was found.
The molybdite occurs as fine very light greenish yellow to nearly colourless flat needles or thin plates, up to
5 mm across, forming irregular aggregates. Some crystals of molybdite as well as vein
quartz and greisen in their
vicinity are coated with fine yellow earthy betpakdalite. No other
minerals are associated with molybdite.
Molybdite is a product of alteration of molybdenite in the
hydrothermal or supergene phase
(AM 49.1497-1498).
At the Cookes Peak Mining District, Luna county, New Mexico, USA. molybdite was found associated with
ilsemannite, sidwillite and
jordisite. It occurs as attractive, well-formed colourless to white sprays
of acicular needles growing in millimeter-sized cavities
(R&M 94.3.233).
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