mineral

Blue Sapphire

Corundum (Al2O3)

Hardness: 9 on the Mohs scale; Color: Deep blue; Luster: Vitreous (glassy); Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.95-4.03.

Hardness: 9 on the Mohs scale
Color: Deep blue
Luster: Vitreous (glassy)

Identified March 17, 2026More mineral →

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Physical properties

Hardness: 9 on the Mohs scale; Color: Deep blue; Luster: Vitreous (glassy); Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.95-4.03.

Formation & geological history

Formed in metamorphic or igneous rocks such as marble, basalt, or pegmatites under high pressure and temperature. Found globally in deposits spanning various geological eras, notably following the uplift of mountain ranges.

Uses & applications

Primary use is in high-end jewelry as a gemstone. Industrial uses include watch crystals, high-durability windows, and abrasive compounds due to its extreme hardness.

Geological facts

Sapphire is the second hardest natural mineral on Earth after diamond. While typically blue, corundum comes in every color; all colors except red (which is Ruby) are classified as sapphires.

Field identification & locations

Identify in the field by its inability to be scratched by steel or quartz. Common locations include Sri Lanka, Madagascar, Myanmar (Burma), and Montana (USA). For collectors, look for clarity, saturation of color, and 'silk' inclusions.