mineral

Blue Sapphire (faceted in jewelry)

Corundum (Al2O3)

Hardness: 9 on the Mohs scale. Color: Deep blue to navy. Luster: Vitreous (glassy). Crystal structure: Trigonal/Hexagonal. Cleavage: None (has parting). Specific Gravity: 3.95–4.03.

Hardness: 9 on the Mohs scale
Color: Deep blue to navy
Luster: Vitreous (glassy)

Identified March 20, 2026More mineral →

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Physical properties

Hardness: 9 on the Mohs scale. Color: Deep blue to navy. Luster: Vitreous (glassy). Crystal structure: Trigonal/Hexagonal. Cleavage: None (has parting). Specific Gravity: 3.95–4.03.

Formation & geological history

Formed through regional or contact metamorphism of aluminum-rich rocks, or found in igneous rocks such as syenite. Large deposits are typically found in alluvial (riverbed) secondary deposits.

Uses & applications

Primarily used in high-end jewelry (rings, bracelets, necklaces). Industrial uses include scratch-resistant watch crystals, high-durability windows, and abrasive tools.

Geological facts

Sapphire is the second hardest natural substance on Earth after diamond. While blue is most famous, sapphires occur in every color except red (which is classified as ruby). Many blue sapphires undergo heat treatment to enhance color and clarity.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by steel or quartz) and high density. Commonly mined in Sri Lanka, Madagascar, Myanmar, and Australia. Collectors look for 'cornflower' or 'royal' blue hues with high transparency.

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