mineral

Ruby

Corundum (Al2O3 with Chromium traces)

Hardness: 9 on Mohs scale; Color: Red (varying from pinkish to blood-red); Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.97-4.05.

Hardness: 9 on Mohs scale
Color: Red (varying from pinkish to blood-red)
Luster: Vitreous to sub-adamantine

Identified April 27, 2026More mineral →

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Physical properties

Formation & geological history

Formed in metamorphic rocks (schists or marbles) or igneous rocks (alkaline basalts or syenites) through high pressure and heat. Often found in secondary alluvial deposits (river gravels).

Uses & applications

Primarily used in high-end jewelry (one of the 'big four' gemstones); also used in laser technology (Ruby lasers) and industrial bearings for watches and precision instruments due to its extreme hardness.

Geological facts

The most prized color is 'pigeon blood' red. Ruby and Sapphire are actually the same mineral (Corundum), distinguished only by their color. Historically, rubies were used in the first functioning laser ever built in 1960.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by anything except diamond), hex-shaped crystal habits, and high specific gravity. Commonly found in Myanmar, Sri Lanka, Thailand, and East Africa.