mineral

Sapphire (Blue)

Corundum (Al2O3)

Hardness: 9 on the Mohs scale. Color: Deep royal blue. Luster: Vitreous to sub-adamantine. Crystal Structure: Hexagonal (Trigonal). Cleavage: None (parting sometimes present). Specific Gravity: 3.95 - 4.10.

Hardness: 9 on the Mohs scale
Color: Deep royal blue
Luster: Vitreous to sub-adamantine

Identified June 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed in metamorphic rocks (schist, gneiss) or igneous rocks (alkaline basalts, syenites) under high pressure and temperature. Large crystals are often found in alluvial deposits (placer deposits).

Uses & applications

Primarily used in fine jewelry and high-end collecting. Industrial sapphires (mostly synthetic) are used for scratch-resistant windows, watch crystals, and high-precision instruments.

Geological facts

Sapphire is the second hardest natural substance on Earth after diamond. While typically blue, the mineral Corundum can be any color except red (which is classified as Ruby). The Blue Giant of the Orient is one of the world's most famous specimens.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by steel or quartz) and high density. Commonly found in Sri Lanka, Madagascar, Myanmar, and Montana. Note: Image appears to show a piece of costume jewelry, which may contain glass or synthetic imitations.