mineral

Blue Sapphire

Corundum (Al2O3 - Aluminum Oxide)

AI-generated identification · may be incorrect

Hardness: 9 on Mohs scale; Color: Cornflower blue to deep navy (inclusion-dependent); Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: None (has parting); Specific Gravity: 3.95-4.03

Hardness: 9 on Mohs scale
Color: Cornflower blue to deep navy (inclusion-dependent)
Luster: Vitreous (glassy)

Identified March 26, 2026More mineral →

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Physical properties

Formation & geological history

Formed in aluminum-rich metamorphic rocks (schists and gneisses) or igneous rocks (pegmatites) under high pressure and temperature. Often found in secondary alluvial deposits (riverbeds) after erosion from host rock.

Uses & applications

Primary use in fine jewelry as a precious gemstone. Industrial applications include watch cristals, high-durability windows, and abrasive compounds due to extreme hardness.

Geological facts

Sapphire is the second hardest natural mineral after diamond. Red corundum is called Ruby; all other colors are called Sapphires. The blue color is typically caused by trace amounts of Iron and Titanium.

Field identification & locations

Identify in the field by its high density (feels heavy for its size) and ability to scratch almost any other mineral. Common sources include Sri Lanka, Madagascar, Myanmar (Burma), and Montana, USA. Collectors look for 'silk' (fine rutile inclusions) which helps prove natural origin.