mineral

Blue Sapphire

Corundum (Al2O3)

Hardness: 9 on Mohs scale; Color: Deep blue (due to iron and titanium traces); Luster: Vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.95–4.03.

Hardness: 9 on Mohs scale
Color: Deep blue (due to iron and titanium traces)
Luster: Vitreous

Identified April 23, 2026More mineral →

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Physical properties

Hardness: 9 on Mohs scale; Color: Deep blue (due to iron and titanium traces); Luster: Vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.95–4.03.

Formation & geological history

Formed in aluminum-rich igneous (pegmatites) or metamorphic rocks (marbles and schists) under high pressure and temperature. Also found in secondary alluvial deposits (gem gravels).

Uses & applications

Primary use is in high-end jewelry. Industrial uses include scratch-resistant windows, infrared optical components, and watch crystals (synthetic).

Geological facts

Sapphire is the birthstone for September. It is the second hardest natural substance on Earth after diamond. Famous specimens include the 'Star of India' and the 'Logan Sapphire'.

Field identification & locations

Identify by its extreme hardness (will scratch glass and steel easily) and high density. Commonly found in Sri Lanka, Madagascar, Myanmar, and Montana (USA). Look for hexagonal barrel-shaped crystals in the field.