gemstone

Blue Sapphire

Corundum (Al2O3 with trace amounts of Fe and Ti)

Hardness: 9 on the Mohs scale, Color: Blue (varies due to iron and titanium impurities), Luster: Adamantine to vitreous, Crystal Structure: Trigonal, Cleavage: None (parts along parting planes), Specific Gravity: 3.98 - 4.1

Identified July 28, 2026More gemstone →

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Physical properties

Formation & geological history

Forms in metamorphic rocks such as marble, or in igneous rocks like basalt and syenite pegmatites, as well as alluvial secondary deposits.

Uses & applications

Used primarily in fine jewelry, watch components, and scientific instruments due to its extreme hardness.

Geological facts

Sapphire is the September birthstone. The most famous sapphires originate from Kashmir, Myanmar, and Sri Lanka.

Field identification & locations

Identified by its high Mohs hardness (scratches quartz, can only be scratched by diamond), high specific gravity, and distinctive hexagonal growth zoning or inclusions when examined under magnification.

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