mineral

Ruby (Raw Corundum)

Corundum (Al2O3:Cr)

Hardness: 9 on Mohs scale; Color: Pink to blood-red; Luster: Adamantine to vitreous; Crystal Structure: Hexagonal/Trigonal; Specific Gravity: 3.97-4.05; No true cleavage.

Hardness: 9 on Mohs scale
Color: Pink to blood-red
Luster: Adamantine to vitreous

Identified June 5, 2026More mineral →

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Physical properties

Hardness: 9 on Mohs scale; Color: Pink to blood-red; Luster: Adamantine to vitreous; Crystal Structure: Hexagonal/Trigonal; Specific Gravity: 3.97-4.05; No true cleavage.

Formation & geological history

Formed in metamorphic or igneous rocks like marble, basalt, or gneiss, often under high pressure and temperature where aluminum is present without silica. Found in various geological ages ranging from Precambrian to Cenozoic.

Uses & applications

Primarily used in jewelry as a precious gemstone. Industrial uses include lasers, waterjet cutters, and watch bearings due to extreme hardness.

Geological facts

The red color comes from chromium. It is the hardest natural mineral after diamond. Some rubies exhibit 'asterism' or a star effect caused by needle-like rutile inclusions.

Field identification & locations

Identify in the field by its distinct hexagonal crystal habit, extreme hardness (scratches almost everything except diamond), and high density. Commonly found in Myanmar, Sri Lanka, Thailand, and Madagascar.