Rock Identifier
Blue Sapphire (Raw/Tumbled Corundum) (Corundum (Aluminum Oxide, Al2O3 with Fe/Ti traces)) — mineral
mineral

Blue Sapphire (Raw/Tumbled Corundum)

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

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 More mineral →

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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.

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