mineral

Blue Sapphire

Corundum (Al2O3) with iron and titanium impurities

Hardness: 9 on Mohs scale; Color: Deep blue (cornflower to royal blue); Luster: Vitreous to adamantine; Crystal system: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.95-4.03

Hardness: 9 on Mohs scale
Color: Deep blue (cornflower to royal blue)
Luster: Vitreous to adamantine

Identified March 31, 2026More mineral →

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Physical properties

Hardness: 9 on Mohs scale; Color: Deep blue (cornflower to royal blue); Luster: Vitreous to adamantine; Crystal system: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.95-4.03

Formation & geological history

Formed in metamorphic rocks like marble or gneiss, and igneous rocks like syenite and pegmatite under high pressure and temperature; often found in secondary alluvial deposits (river beds).

Uses & applications

High-end jewelry, industrial abrasives, watch crystals, and high-durability windows for cameras or sensors.

Geological facts

The blue color is caused by intervalence charge transfer between iron (Fe2+) and titanium (Ti4+) ions in the crystal lattice. Most sapphires undergo heat treatment to enhance color and clarity.

Field identification & locations

Identify by its extreme hardness (scratches almost everything except diamond) and density. Found in Sri Lanka, Madagascar, Myanmar, and Montana (USA). Collectors look for 'silk' inclusions to verify natural origin.

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