Image: James St. John (CC BY 2.0)
trigonalcommonOxides
Corundum
Al2O3
The image displays numerous rough, elongated to blocky corundum crystals, predominantly in shades of reddish-brown and grey-brown, with some showing hints of pink or purple. Their surfaces are typically dull and weathered.
Corundum Physical Properties
Mohs Hardness
9Crystal System
trigonalStreak Color
WhiteCleavage
None, but often exhibits basal and rhombohedral partingFracture
Conchoidal to unevenSpecific Gravity
4Colors
reddish-brown, grey-brown, pink, blue, yellow, green, colorlessTransparency
Translucent to opaqueType Locality
IndiaMineral Group
OxidesUses
abrasives, gemstones, industrial applications, collector specimensAssociated Minerals
feldspar, mica, garnet, kyanite, sillimaniteRarity
commonGeological Context
Corundum forms in aluminum-rich metamorphic rocks like schists and gneisses, as well as some igneous rocks such as syenites and pegmatites. It is also commonly found in placer deposits due to its high hardness and resistance to weathering.
