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 11, 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 metamorphic rocks (schists, gneisses) and igneous rocks (syenites, pegmatites) under high pressure and temperature. Found in gemstone-bearing gravels (alluvial deposits) or primary crystalline rock.

Uses & applications

High-end jewelry, watch crystals, industrial abrasives, optical components, and precision instruments.

Geological facts

Sapphire is the second hardest natural substance after diamond. The color ranges from pale to deep 'Royal Blue'. It is the birthstone for September.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by steel or quartz) and heavy weight for its size. Most often found in river beds or primary deposits in Sri Lanka, Madagascar, and Kashmir.