gemstone

Blue sapphire (rough corundum)

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

AI-generated identification · may be incorrect

Likely a small rough crystal, deep blue with vitreous luster; Mohs hardness 9, trigonal crystal structure, no true cleavage, specific gravity about 4.0. The photo alone cannot confirm its identity or quality.

Identified October 13, 2026More gemstone →

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Physical properties

Formation & geological history

Forms in aluminum-rich, silica-poor rocks, including metamorphic marbles and gneisses and some igneous rocks; geological ages vary widely. Blue color develops from trace-element substitutions in the crystal lattice.

Uses & applications

Used in jewelry and as a durable abrasive or industrial material; synthetic sapphire is used in watch crystals and technical components.

Geological facts

Sapphire is the gem variety of corundum; red corundum is ruby. Natural sapphire is often heat-treated to improve color and clarity.

Field identification & locations

Common sources include Sri Lanka, Madagascar, Myanmar, Australia, and Kashmir. Identification requires testing: hardness and density help distinguish it, but gemological examination is needed to verify natural origin and treatments.