Gem-name guide / Gem variety

Ruby

Al₂O₃

Ruby is the red gem variety of corundum. Chromium is responsible for its red colour. A ruby and a sapphire belong to the same mineral species; the gem names describe different colour varieties.

Material or mineral family: Corundum
Name classification: Gem variety
Mohs hardness: 9
Typical colour: Red

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Names describe materials, not the authenticity, treatment, provenance or quality of a particular specimen. Physical properties vary for mixed materials; values absent from this guide have not been estimated.

Reference snapshot: September 2026. Source dates and uncertainties are retained in the record.