Gem-name guide / Gem variety

Sapphire

Al₂O₃

Sapphire is gem-quality corundum outside the ruby-red range. Alongside blue stones, the family includes yellow, green, violet, orange and pink varieties. Some examples show colour change or a star-like optical effect.

Material or mineral family: Corundum
Name classification: Gem variety
Mohs hardness: 9
Typical colour: Blue and other colours except ruby 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.