mineral

Corundum (Ruby variety)

Aluminium oxide (Al2O3)

Hardness: 9 on Mohs scale; Color: Red to purplish-pink; Luster: Adamantine to vitreous; Crystal structure: Trigonal/Hexagonal barrel-shaped crystals; Cleavage: None (has parting); Specific Gravity: 3.95–4.10

Hardness: 9 on Mohs scale
Color: Red to purplish-pink
Luster: Adamantine to vitreous

Identified April 2, 2026More mineral →

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Physical properties

Formation & geological history

Formed in metamorphic rocks seperti schists or gneisses, or in marble, and as a primary mineral in igneous rocks like syenite. It typically occurs when magma cools slowly or through regional metamorphism at high pressure and temperature.

Uses & applications

Used primarily as a gemstone in jewelry (Rubies). Industrial versions are used as abrasives, in sandpaper, and for laser technology due to high hardness and thermal conductivity.

Geological facts

Corundum is the second hardest natural mineral known to man, trailing only diamond. Ruby is the red variety of corundum, while all other colors are known as sapphire.

Field identification & locations

Identify in the field by its extreme hardness (will scratch almost anything except diamond) and its characteristic hexagonal crystal habit. Found commonly in Myanmar, Sri Lanka, Thailand, and parts of Madagascar.