mineral

Blue Sapphire (Raw/Tumbled Corundum)

Corundum (Aluminum Oxide, Al2O3 with Fe/Ti traces)

AI-generated identification · may be incorrect

Hardness: 9.0 on Mohs scale; Color: Indigo to royal blue; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Specific Gravity: 3.95-4.10; Cleavage: None (conchoidal fracture).

Hardness: 9
Color: Indigo to royal blue
Luster: Vitreous to sub-adamantine

Identified June 18, 2026More mineral →

Explore Blue Sapphire (Raw/Tumbled Corundum) in the encyclopedia →

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Physical properties

Hardness: 9.0 on Mohs scale; Color: Indigo to royal blue; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Specific Gravity: 3.95-4.10; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed in aluminum-rich igneous rocks like syenites or pegmatites and metamorphic rocks like marble or schist. Often found in alluvial deposits (placer mining) as water-worn pebbles due to high density and hardness.

Uses & applications

Used extensively in gemstone jewelry, precision instruments, scratch-resistant watch crystals, and high-strength industrial abrasives.

Geological facts

Sapphire is the second hardest natural mineral after diamond. It is the birthstone for September and has been historically associated with royalty and wisdom. Trace amounts of iron and titanium create the blue color.

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. Look for hexagonal crystal habits or barrel-shaped water-worn pebbles.