mineral

Ruby

Corundum (Al2O3 with Chromium traces)

Hardness: 9.0 on Mohs scale; Color: Pinkish-red to deep pigeon-blood red; Luster: Vitreous to sub-adamantine; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.97-4.05

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

Identified March 10, 2026More mineral →

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Physical properties

Formation & geological history

Formed in metamorphic rocks (schists or marbles) and igneous rocks (syenites) where aluminum is plentiful and silica is absent. High-pressure/high-temperature environments, often millions of years old.

Uses & applications

Primary use in fine jewelry and high-end luxury goods. Industrial rubies (often synthetic) are used in lasers, watch bearings, and high-precision instruments.

Geological facts

Ruby is the red variety of the mineral species corundum; all other colors are called sapphire. Its name comes from 'ruber', Latin for red. It is the birthstone for July and the most valuable variety of the corundum family.

Field identification & locations

Identify by its extreme hardness (scratches almost everything but diamond) and vibrant red fluorescence under UV light. Often found in alluvial deposits in Myanmar, Sri Lanka, Madagascar, and Thailand.