gemstone

Ruby (Raw Corundum)

Alumina (Al2O3) with Chromium traces

Hardness: 9 (Mohs scale); Color: Pinkish-red to deep red; Luster: Adamantine to vitreous (sub-metallic when raw); Crystal structure: Hexagonal/Trigonal (often barrel-shaped); Specific gravity: 3.97-4.05

Hardness: 9 (Mohs scale)
Color: Pinkish-red to deep red
Luster: Adamantine to vitreous (sub-metallic when raw)

Identified July 20, 2026More gemstone →

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Physical properties

Formation & geological history

Formed in metamorphic or igneous environments, specifically marble-hosted or basalt-hosted deposits. Most form under high pressure and temperature during mountain-building events (Orogeny).

Uses & applications

Jewelry, industrial abrasives, lasers, and precision bearings in watches. Raw specimens are highly popular among mineral collectors.

Geological facts

Ruby is the red variety of the mineral corundum; all other colors are called sapphire. It is the second hardest natural substance on Earth after diamond. The red color comes from chromium replacing aluminum in the crystal lattice.

Field identification & locations

Identify by its hexagonal barrel shape, extreme hardness (it will scratch glass and almost all other minerals), and red color. Found in Myanmar, Madagascar, India, and Afghanistan.

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