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 (has parting); Specific Gravity: 3.97-4.05

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

Identified June 6, 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 (has parting); Specific Gravity: 3.97-4.05

Formation & geological history

Formed under intense heat and pressure in the Earth's crust, typically in metamorphic rocks like marble or as an accessory mineral in igneous rocks like basalt. Some are found in alluvial deposits.

Uses & applications

Primarily used in high-end jewelry, watch bearings (synthetic), and historical use in early laser technology.

Geological facts

The most valuable rubies come from the Mogok Valley in Myanmar (Burma), known as 'Pigeon's Blood' rubies for their deep red color.

Field identification & locations

Identified by its extreme hardness and fluorescent properties under UV light. Found in Myanmar, Thailand, Sri Lanka, and Madagascar. Look for the 'silk' (rutile inclusions) to distinguish natural from synthetic specimens.