mineral

Ruby (Corundum)

Aluminum Oxide (Al2O3) with Chromium traces

Hardness: 9.0 (Mohs scale), Color: Vivid red to pinkish-red, Luster: Vitreous to sub-adamantine, Crystal structure: Trigonal/Hexagonal, Cleavage: None (has parting), Specific Gravity: 3.97-4.05

Hardness: 9

Identified April 8, 2026More mineral →

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Physical properties

Hardness: 9.0 (Mohs scale), Color: Vivid red to pinkish-red, Luster: Vitreous to sub-adamantine, Crystal structure: Trigonal/Hexagonal, Cleavage: None (has parting), Specific Gravity: 3.97-4.05

Formation & geological history

Formed in metamorphic rocks (marble or schist) or igneous rocks (basalt) where aluminum-rich fluids crystallized under high heat and pressure, often millions of years ago.

Uses & applications

Primarily used in high-end jewelry (one of the four precious stones), watchmaking (pivot bearings), and industrial lasers.

Geological facts

Ruby is the red variety of the mineral corundum; sapphire is any other color of corundum. The most valuable rubies exhibit a 'pigeon blood' red color and a natural fluorescence.

Field identification & locations

Identify in the field by its extreme hardness (scratches almost anything except diamond) and hexagonal crystal habit. Common locations include Myanmar (Burma), Mozambique, Thailand, and Sri Lanka.

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