Image: James St. John (CC BY 2.0)
trigonaluncommonOxides
Sapphire
Al2O3
A transparent, typically blue, precious gemstone, often faceted for jewelry. The image shows a brilliant blue, faceted sapphire.
Sapphire Physical Properties
Mohs Hardness
9Crystal System
trigonalLuster
vitreousStreak Color
whiteCleavage
None (parting often present)Fracture
conchoidalSpecific Gravity
3.95Colors
blue, yellow, pink, purple, green, orange, black, colorlessTransparency
transparentType Locality
Sri Lanka, Madagascar, Australia, Thailand, Montana (USA), KashmirMineral Group
OxidesUses
jewelry, industrial abrasives, watch bearings, scientific instrumentsAssociated Minerals
kyanite, sillimanite, garnet, spinel, feldspar, micaRarity
uncommonGeological Context
Sapphire forms in igneous rocks (such as basalt and syenite) and metamorphic rocks (like gneiss and schist) in aluminum-rich environments. It is also commonly found in alluvial deposits due to its hardness and resistance to weathering.
