mineral

Rough Ruby

Corundum (Al2O3) with Chromium traces

Hardness: 9.0 on Mohs scale; Color: Pinkish-red to deep pigeon-blood red; Luster: Adamantine to vitreous; 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: Adamantine to vitreous

Identified March 30, 2026More mineral →

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Physical properties

Formation & geological history

Formed in metamorphic rocks such as mica schist or gneiss, or in marble through contact metamorphism. Often found as water-worn pebbles in alluvial deposits (placer deposits) originating from the Tertiary period to the present.

Uses & applications

Primary use is in high-end jewelry (faceted or cabochons). Industrial (non-gem quality) rubies are used for watch bearings, lasers, and high-strength abrasives.

Geological facts

Ruby is the red variety of the mineral corundum; all other colors are called sapphire. It is one of the four precious stones along with diamond, emerald, and sapphire. Rubies often show strong red fluorescence under UV light due to chromium content.

Field identification & locations

Identify in the field by its extreme hardness (cannot be scratched by steel or quartz) and its high density. Found commonly in Southeast Asia (Myanmar, Vietnam), East Africa (Mozambique, Madagascar), and South Asia (India, Sri Lanka).