mineral

Ruby

Corundum (Al2O3)

Hardness: 9 on Mohs scale; Color: Red (due to chromium); Luster: Vitreous to sub-adamantine; Crystal structure: Trigonal/Hexagonal; Cleavage: None; Specific gravity: 3.97-4.05

Hardness: 9 on Mohs scale
Color: Red (due to chromium)
Luster: Vitreous to sub-adamantine

Identified June 12, 2026More mineral →

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Physical properties

Hardness: 9 on Mohs scale; Color: Red (due to chromium); Luster: Vitreous to sub-adamantine; Crystal structure: Trigonal/Hexagonal; Cleavage: None; Specific gravity: 3.97-4.05

Formation & geological history

Formed in metamorphic rocks such as marble or gneiss, and occasionally in igneous rocks. They are often found in alluvial deposits. Geological age varies greatly from millions to over a billion years old.

Uses & applications

Primary use is in high-end jewelry. Also used for industrial purposes including lasers, precision bearings, and watch parts due to extreme hardness.

Geological facts

Ruby is one of the four precious gemstones. The most valuable color is a deep red known as 'pigeon blood.' It is the birthstone for July.

Field identification & locations

Identified by its distinctive red color, extreme hardness (scratches almost everything but diamond), and specific gravity. Common locations include Myanmar, Sri Lanka, Thailand, and Madagascar.