gemstone

Sapphire

Corundum (Al2O3) with traces of Iron and Titanium

AI-generated identification · may be incorrect

Hardness: 9 on the Mohs scale. Color: Deep blue (cornflower to royal blue). Luster: Vitreous to sub-adamantine. Crystal structure: Hexagonal/Trigonal. Specific gravity: 3.95-4.03.

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

Identified July 9, 2026More gemstone →

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Physical properties

Hardness: 9 on the Mohs scale. Color: Deep blue (cornflower to royal blue). Luster: Vitreous to sub-adamantine. Crystal structure: Hexagonal/Trigonal. Specific gravity: 3.95-4.03.

Formation & geological history

Formed in igneous or metamorphic environments such as marble, basalt, or pegmatite. Frequently found in secondary alluvial (placer) deposits after weathering from primary host rock.

Uses & applications

Primarily used in high-end jewelry (rings, bracelets, necklaces). Industrial uses include watch crystals, high-durability windows, and abrasive tools due to its extreme hardness.

Geological facts

Sapphire is the birthstone for September. The most famous sapphires include the Star of India and the Logan Sapphire. While blue is most common, sapphires can occur in any color except red (which is classified as ruby).

Field identification & locations

Identified in the field by its high specific gravity, hexagonal crystal habit, and extreme hardness (scratching quartz or topaz). Major sources include Kashmir, Myanmar (Burma), Sri Lanka, Madagascar, and Thailand.