corundum

From Tamil குருந்தம் (kuruntam, “ruby, sapphire”) First attested in the early 18th century.

• (UK, US) IPA^(key): /kəˈɹʌn.dəm/

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corundum (countable and uncountable, plural corundums)

1. (mineralogy) An extremely hard mineral, a form of aluminum oxide with the chemical formula Al₂O₃, that occurs in the form of the gemstones sapphire and ruby; it is used as an abrasive.

• David Barthelmy (1997–2025), “Corundum”, in Webmineral Mineralogy Database.
• “corundum”, in Mindat.org‎^[1], Hudson Institute of Mineralogy, 2000–2025.