What is Molybdite?
Molybdite is a subtle but instructive secondary mineral. Its pale yellow coatings show how a metallic sulfide ore continues to react after exposure to oxygen, creating a new mineral generation at the surface.
Mineralogy and crystal structure
Reference formula: MoO3. Molybdite is an orthorhombic molybdenum trioxide and a rare oxidation product of molybdenite. It is commonly fine-grained or powdery, so association with molybdenite and analytical confirmation are important. Molybdite is classified with oxides and has a orthorhombic crystal system. Typical hardness is 1–2 on the Mohs scale and specific gravity is approximately 4.7–4.8.
Colour, lustre and habit
Typical colours include yellow, greenish-yellow, white. The usual platy, scaly, powdery habit and pearly, earthy, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Molybdite forms in or is associated with oxidation of molybdenite in exposed portions of molybdenum-bearing hydrothermal deposits. Important documented localities include the United States, Chile, Canada, Norway, Germany and Armenia.
A yellow oxidation halo around molybdenite
Molybdite is a subtle but instructive secondary mineral. Its pale yellow coatings show how a metallic sulfide ore continues to react after exposure to oxygen, creating a new mineral generation at the surface.
Collecting and care
Very soft and dusty: keep enclosed, dry and undisturbed; avoid inhaling powder.
