mineral

Ruby

Corundum (Al2O3:Cr)

Hardness: 9 on Mohs scale; Color: Red (varying from pinkish to blood-red); Luster: Adamantine to vitreous; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (has parting); Specific Gravity: 3.97–4.05

Hardness: 9 on Mohs scale
Color: Red (varying from pinkish to blood-red)
Luster: Adamantine to vitreous

Identified March 13, 2026More mineral →

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Physical properties

Formation & geological history

Formed in metamorphic or igneous environments, most commonly in marble or basalt. The red color is caused by the presence of Chromium (Cr) replacing Aluminum in the crystal lattice. Famous deposits like those in Myanmar occurred roughly 25-50 million years ago during the Himalayan orogeny.

Uses & applications

Primary use in high-end jewelry (one of the four precious stones), industrial applications include lasers (ruby lasers), watch bearings, and precision instruments due to its extreme hardness.

Geological facts

The word 'ruby' comes from 'ruber', Latin for red. Large flawless rubies are rarer and often more expensive than diamonds of the same size. Rubies show strong red fluorescence under UV light, which enhances their color in sunlight.

Field identification & locations

Identify in the field by its extreme hardness (scratches everything but diamond), hexagonal crystal shape, and characteristic red color. Commonly found in Myanmar, Sri Lanka, Thailand, and Mozambique. Collectors look for 'pigeon blood' red color and high transparency.