mineral

Ruby

Corundum (Al2O3 with Chromium traces)

Hardness: 9 on Mohs scale; Color: Pinkish-red to deep blood-red; Luster: Adamantine to vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None; Specific Gravity: 3.97-4.05

Hardness: 9 on Mohs scale
Color: Pinkish-red to deep blood-red
Luster: Adamantine to vitreous

Identified March 25, 2026More mineral →

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Physical properties

Hardness: 9 on Mohs scale; Color: Pinkish-red to deep blood-red; Luster: Adamantine to vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None; Specific Gravity: 3.97-4.05

Formation & geological history

Formed in metamorphic rocks (schists or marbles) or igneous rocks (basalt) through contact or regional metamorphism at high pressure and temperature. Primary sources are Cenozoic to Precambrian in age.

Uses & applications

Primarily used as a gemstone in high-end jewelry. Industrial uses include lasers, precision bearings in mechanical watches, and medical equipment.

Geological facts

Ruby is the red variety of the mineral corundum; every other color of corundum is called sapphire. The presence of chromium gives it the red color and can also cause it to fluoresce under UV light.

Field identification & locations

Identify by extreme hardness (scratches almost everything but diamond) and high density. Found in Myanmar (Burma), Sri Lanka, Thailand, and Madagascar. Look for silk-like inclusions and pleochroism.