gemstone

Blue sapphire (faceted gemstone)

Corundum, Al₂O₃; blue color typically from trace iron and titanium

AI-generated identification · may be incorrect

Mohs hardness 9; blue to dark blue, vitreous luster, trigonal crystal structure, no true cleavage. The pictured stone is a faceted cut gem; its identity cannot be confirmed from appearance alone.

Identified October 11, 2026More gemstone →

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Physical properties

Mohs hardness 9; blue to dark blue, vitreous luster, trigonal crystal structure, no true cleavage. The pictured stone is a faceted cut gem; its identity cannot be confirmed from appearance alone.

Formation & geological history

Forms in aluminum-rich, silica-poor rocks and in metamorphic or igneous settings; sapphires may be billions of years old and are often concentrated in secondary alluvial deposits.

Uses & applications

Used in jewelry and, because of its hardness, in watch crystals, precision components, and abrasives.

Geological facts

Sapphire is the gem variety of corundum; red corundum is called ruby.

Field identification & locations

Common sources include Sri Lanka, Madagascar, Myanmar, Australia, and Kashmir. Field identification relies on exceptional hardness and gemological testing; appearance alone cannot distinguish natural, synthetic, or imitation stones.