mineral

Blue Sapphire (in a faceted jewelry setting)

Corundum (Al2O3) with trace Iron and Titanium

Hardness: 9.0 (Mohs scale); Color: Deep blue; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: None (has parting); Specific Gravity: 3.98 - 4.06

Hardness: 9
Color: Deep blue
Luster: Vitreous (glassy)

Identified March 17, 2026More mineral →

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Physical properties

Hardness: 9.0 (Mohs scale); Color: Deep blue; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (Trigonal); Cleavage: None (has parting); Specific Gravity: 3.98 - 4.06

Formation & geological history

Formed in metamorphic or igneous environments, particularly in marble, granulite, or syenite. It typically occurs as a result of contact or regional metamorphism of aluminum-rich rocks.

Uses & applications

Primarily used as a precious gemstone in jewelry. Industrial-grade sapphire (synthetic) is used for watch crystals, high-durability windows, and electronics.

Geological facts

Sapphire is the second hardest natural mineral after diamond. The blue color is specifically caused by inter-valence charge transfer between iron and titanium ions within the crystal lattice.

Field identification & locations

Identification in the field is based on its hexagonal barrel-shaped crystals, extreme hardness (scratches topaz), and high density. Commonly found in alluvial deposits in Sri Lanka, Madagascar, and Myanmar.

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