Molybdite

molybdite

ilsemannite

sidwillite

jordisite

Images

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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