mineral

Raw Ruby (Corundum)

Corundum (Aluminum Oxide, Al2O3)

AI-generated identification · may be incorrect

Mohs hardness of 9.0; color range from pinkish-red to deep pigeon-blood red; vitreous to adamantine luster; hexagonal (trigonal) crystal system; no true cleavage but shows parting.

Identified July 17, 2026More mineral →

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Physical properties

Mohs hardness of 9.0; color range from pinkish-red to deep pigeon-blood red; vitreous to adamantine luster; hexagonal (trigonal) crystal system; no true cleavage but shows parting.

Formation & geological history

Formed via regional or contact metamorphism of aluminum-rich rocks (shales, limestones) or in igneous environments such as syenites. Found in marble deposits and alluvial gravels.

Uses & applications

Used primarily in jewelry as a precious gemstone; industrial grades are used for abrasives, watch bearings, and laser production.

Geological facts

Ruby is the red variety of corundum; all other colors are called sapphire. It is the second hardest natural mineral after diamond. Some rubies exhibit asterism (the star effect) when cut as cabochons.

Field identification & locations

Identified in the field by its extreme hardness (will scratch glass and quartz easily) and its hexagonal barrel-shaped crystal habit. Common in Myanmar, Sri Lanka, Madagascar, and East Africa.