gemstone

Polished ruby cabochon (likely synthetic or treated)

Corundum, aluminum oxide (Al₂O₃), colored red by chromium

AI-generated identification · may be incorrect

Mohs hardness 9; red to purplish-red color, vitreous luster, trigonal crystal structure, and no true cleavage. The smooth domed cut is a cabochon; visible inclusions or fractures may indicate natural material, treatment, or synthesis.

Identified August 23, 2026More gemstone →

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Physical properties

Formation & geological history

Ruby forms mainly in metamorphic rocks such as marble and metabasite, with some magmatic sources; natural crystals range from Precambrian to younger geological ages. Its red color results primarily from chromium substituting into corundum.

Uses & applications

Used in jewelry, watch bearings, lasers, abrasives, and scientific instruments. Fine transparent natural rubies can be highly valuable, while opaque or synthetic cabochons are common and affordable.

Geological facts

Ruby and sapphire are varieties of the same mineral, corundum; only red corundum is called ruby. Heat treatment and laboratory synthesis are widespread.

Field identification & locations

Identify by exceptional hardness, strong red color, high luster, and lack of cleavage; ruby may fluoresce vivid red under UV light. Common sources include Myanmar, Mozambique, Sri Lanka, Vietnam, and Madagascar; confirm identity with refractive-index and spectroscopy testing.