Image: James St. John (CC BY 2.0)
cubiccommonOxides
Sapphire
Al2O3
Sapphire is a variety of corundum, typically known for its vibrant blue color, though it occurs in many other hues. It forms as hexagonal crystals, often with a vitreous to adamantine luster.
Sapphire Physical Properties
Mohs Hardness
9Crystal System
cubicLuster
vitreousStreak Color
WhiteCleavage
None, but parting often presentFracture
Conchoidal to unevenSpecific Gravity
4Colors
blue, pink, yellow, green, purple, orange, black, colorlessTransparency
Transparent to translucentType Locality
India, Sri Lanka, Madagascar, Australia, Thailand, USA (Montana)Mineral Group
OxidesUses
jewelry, industrial abrasives, watch bearings, scientific instrumentsAssociated Minerals
feldspar, mica, garnet, spinel, kyaniteRarity
commonGeological Context
Sapphire forms in various geological environments, including metamorphic rocks (like gneiss and schist), igneous rocks (such as basalt and syenite), and often accumulates in alluvial deposits due to its high hardness and resistance to weathering.
