mineral

Ruby

Corundum (Aluminium Oxide with Chromium impurities, Al2O3:Cr)

Hardness: 9.0 (Mohs scale); Color: Pinkish-red to pigeon-blood red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Specific Gravity: 3.97-4.05; No true cleavage.

Hardness: 9
Color: Pinkish-red to pigeon-blood red
Luster: Vitreous to sub-adamantine

Identified April 8, 2026More mineral →

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Physical properties

Hardness: 9.0 (Mohs scale); Color: Pinkish-red to pigeon-blood red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Specific Gravity: 3.97-4.05; No true cleavage.

Formation & geological history

Formed through regional or contact metamorphism of aluminum-rich rocks (like marble or basalt) or as a primary mineral in igneous rocks like syenite. Significant deposits are found in marble-hosted environments like those in Myanmar.

Uses & applications

Primarily used as a gemstone in high-end jewelry. Industrial-grade rubies (often synthetic) are used in lasers, watchmaking (jewel bearings), and precision instruments due to their hardness and optical properties.

Geological facts

Ruby is the red variety of the mineral corundum; all other colors are called sapphire. It is one of the four traditional 'precious' stones. The red color is caused by the presence of chromium, which also causes the fluorescence found in many rubies.

Field identification & locations

Identify by its exceptional hardness (it can scratch almost any other mineral except diamond) and its distinct red streak. Collectors look for 'pigeon blood' color and clarity. Common locations include Myanmar, Thailand, Sri Lanka, and Madagascar.

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