gemstone

Ruby

Corundum (Aluminum Oxide, Al2O3)

Hardness: 9 on Mohs scale; Color: Deep red (pigeon blood); Luster: Vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 3.97-4.05

Hardness: 9 on Mohs scale
Color: Deep red (pigeon blood)
Luster: Vitreous

Identified July 16, 2026More gemstone →

Explore Ruby in the encyclopedia →

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: Deep red (pigeon blood); Luster: Vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 3.97-4.05

Formation & geological history

Formed in metamorphic or igneous environments under high heat and pressure, typically in marble or basalt deposits. Geological age ranges from Precambrian to Tertiary.

Uses & applications

Primary use in high-end jewelry and luxury collecting; industrial uses include watch bearings, lasers, and precision instruments due to its extreme hardness and thermal conductivity.

Geological facts

Ruby is one of the four traditional 'precious' stones. The red color is caused specifically by the presence of chromium. It is the birthstone for July and represents the 40th wedding anniversary.

Field identification & locations

Identify by its deep red color and extreme hardness (scratching quartz/topaz). Commonly found in Myanmar (Burma), Sri Lanka, Madagascar, and Thailand. Collectors look for clarity and saturation of red.