mineral

Blue Sapphire

Corundum (Al2O3)

Hardness: 9 on Mohs scale; Color: Deep blue (the 'primary' color for sapphires caused by iron and titanium); Luster: Adamantine to vitreous; Crystal Structure: Trigonal; Cleavage: None (has parting); Specific Gravity: 3.98–4.06.

Hardness: 9 on Mohs scale
Luster: Adamantine to vitreous

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed in aluminum-rich metamorphic rocks (schists/gneisses) or igneous rocks (syenites/pegmatites). Common in alluvial deposits where heavy minerals settle. Most geological deposits range from 500 million to a billion years old.

Uses & applications

Primarily used as a gemstone in high-end jewelry. Industrial varieties (synthetic sapphire) are used for scratch-resistant watch crystals, optical components, and abrasives.

Geological facts

Sapphire is the second hardest natural substance after diamond. The blue variety is the most famous, but sapphires come in every color except red (red corundum is classified as ruby).

Field identification & locations

Identify by its extreme hardness (cannot be scratched by steel or quartz) and high density. Commonly found in Sri Lanka, Madagascar, Myanmar, and Montana (USA). Collectors look for 'cornflower' or 'royal' blue shades with high clarity.