Corundum
Image: James St. John (CC BY 2.0)
Mineral NameCorundum
Chemical FormulaAl2O3
Mohs Hardness9
Crystal Systemtrigonal
Streak ColorWhite
CleavageNone, but often exhibits basal and rhombohedral parting
FractureConchoidal to uneven
Specific Gravity4
Colorsreddish-brown, grey-brown, pink, blue, yellow, green, colorless
TransparencyTranslucent to opaque
Type LocalityIndia
Mineral GroupOxides
Usesabrasives, gemstones, industrial applications, collector specimens
Associated Mineralsfeldspar, mica, garnet, kyanite, sillimanite
Raritycommon
Description
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.
Geological 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.
