Image: James St. John (CC BY 2.0)
trigonalcommonOxides
Corundum
Al2O3
A dark reddish-brown to purplish-brown, translucent to opaque, barrel-shaped or hexagonal crystal, exhibiting typical corundum morphology.
Corundum Physical Properties
Mohs Hardness
9Crystal System
trigonalLuster
vitreousStreak Color
whiteCleavage
None (parting often present)Fracture
conchoidalSpecific Gravity
3.95Colors
dark red, brown, purpleTransparency
translucentType Locality
IndiaMineral Group
OxidesUses
abrasive, gemstone, industrial, collectorAssociated Minerals
mica, feldspar, kyanite, garnet, spinelRarity
commonGeological Context
Corundum forms in aluminum-rich, silica-poor metamorphic rocks like schists and gneisses, certain igneous rocks such as syenites, and is frequently found in placer deposits due to its exceptional hardness and resistance to weathering.
