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Molybdite on molybdenite from the Questa Molybdenum Mine (size: 11.0 x 6.7 x 4.1 cm)
Category Mineral
(repeating unit)
Strunz classification 4.EA.10
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Pbnm
Unit cell a = 3.96 Å, b = 13.85 Å,
c = 3.69 Å; Z = 4
Color Light greenish yellow to nearly colorless
Crystal habit Flattened needles or thin plates may occur in aggregates
Cleavage Perfect on {100}, district on {001}
Tenacity Flexible
Mohs scale hardness 3 - 4
Luster Adamantine
Streak White
Diaphaneity Transparent
Specific gravity 4.72
Optical properties Biaxial (+)
Birefringence High
2V angle Large
References [1][2][3][4]

Molybdite is the naturally occurring mineral form of molybdenum trioxide MoO3. It occurs as yellow to greenish needles and crystallizes in the orthorhombic crystal system.

Discovery and occurrence[edit]

Molybdite was first described in 1854 for and occurrence in quartz veins in the Knöttel area of Krupka, Krušné Hory Mountains in the Ústí Region of Bohemia, Czech Republic.[3] It occurs in vein cavities and as coatings in molybdenite ore veins and quartz topaz greisens. Associated minerals include molybdenite, betpakdalite and quartz.[2] The similar mineral ferrimolybdite is often misidentified as molybdite.[2]