Molybdite

Molybdite
Molybdite on molybdenite from the Questa Molybdenum Mine (size: 11.0 x 6.7 x 4.1 cm)
General
Category	Mineral
Formula (repeating unit)	MoO3
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
Identification
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

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.

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. It occurs in vein cavities and as coatings in molybdenite ore veins and quartz topaz greisens. Associated minerals include molybdenite, betpakdalite and quartz. The similar mineral ferrimolybdite is often misidentified as molybdite.