mineral

Blue Sapphire

Corundum (Al2O3)

Hardness: 9 on the Mohs scale; Color: Deep blue (due to iron and titanium); Luster: Vitreous (glassy); Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.98 - 4.06

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

Identified January 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed in aluminum-rich metamorphic rocks (gneiss/schist) or igneous rocks (alkaline basalts or syenites) through high pressure and temperature. Commonly found in secondary alluvial deposits (river beds).

Uses & applications

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

Geological facts

Sapphire is the second hardest natural substance on Earth. While blue is most famous, sapphires occur in every color except red (which is classified as ruby).

Field identification & locations

Identify by its ability to scratch almost all other minerals, its high density (feels heavy for its size), and deep saturated color. Commonly sourced from Sri Lanka, Madagascar, Myanmar, and Montana.