mineral

Ruby

Corundum (Al2O3)

Hardness: 9 on Mohs scale; Color: Red (pigeon blood to pinkish-red); Luster: Adamantine to vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None/Parting; Specific Gravity: 3.97-4.05

Hardness: 9 on Mohs scale
Color: Red (pigeon blood to pinkish-red)
Luster: Adamantine to vitreous

Identified May 23, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 9 on Mohs scale; Color: Red (pigeon blood to pinkish-red); Luster: Adamantine to vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None/Parting; Specific Gravity: 3.97-4.05

Formation & geological history

Formed under high-pressure and high-temperature conditions in metamorphic rocks like marble or schist, or in igneous rocks like basalt. Found in alluvial deposits. Geological age varies globally but often associated with ancient tectonic collisions.

Uses & applications

Primary use is in high-end jewelry (faceted gemstones); also used in laser technology and watchmaking (industrial grade synthetic corundum).

Geological facts

Ruby is one of the four traditional 'precious' stones. The red color is caused specifically by the presence of the element chromium. Specimens with a 'star' effect (asterism) are highly prized.

Field identification & locations

Identify by extreme hardness (scratches almost everything except diamond), deep red hue, and internal inclusions (silk). Common locations include Myanmar (Burma), Mozambique, Thailand, and Sri Lanka.