corundum
noun
co·run·dum
kə-ˈrən-dəm 
: a very hard mineral that consists of aluminum oxide occurring in massive and crystalline forms, that can be synthesized, and that is used for gemstones (such as ruby and sapphire) and as an abrasive
Examples of corundum in a Sentence
Recent Examples on the Web
On Earth, corundum typically forms deep within the planet under specific geological conditions tied to tectonic activity.
—
Ryan Brennan, Kansas City Star, 27 Apr. 2026
The difference between the two comes down to trace metals within the corundum, something scientists couldn’t confirm using imaging alone.
—Ryan Brennan, Miami Herald, 27 Apr. 2026
Those high-energy collisions would have generated intense heat and pressure, transforming aluminum-rich surface materials into corundum.
—Ryan Brennan
april 27, Fort Worth Star-Telegram, 27 Apr. 2026
Ruby and sapphire mining began in the area in 1870, once rubies were discovered in the corundum mines.
—Trudy Haywood Saunders, Travel + Leisure, 27 Jan. 2026
Pure corundum is colorless, but trace elements like iron, titanium, chromium, gallium and vanadium give it colors like blue, yellow, red, green, pink, or purple.
—David Bressan, Forbes.com, 26 June 2025
The chromium replaces about 1% of the aluminum in the corundum or beryl crystal when a ruby or emerald forms underground at a high temperature and pressure.
—Daniel Freedman, The Conversation, 4 Feb. 2025
The domed disc is a pink synthetic corundum in the same vein as ruby or sapphire, and the result is a soft, translucent pink that shifts not only depending on viewing angle and lighting.
—Blake Buettner, Robb Report, 8 May 2024
At $950, the luxury wearable is made from black synthetic corundum with 18-karat yellow gold braided torchon detailing and a signature interlocking G logo.
—Sara Klausing, Men's Health, 4 Nov. 2022
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Ryan Brennan, Kansas City Star, 27 Apr. 2026
The difference between the two comes down to trace metals within the corundum, something scientists couldn’t confirm using imaging alone.
—Ryan Brennan, Miami Herald, 27 Apr. 2026
Those high-energy collisions would have generated intense heat and pressure, transforming aluminum-rich surface materials into corundum.
—Ryan Brennan
april 27, Fort Worth Star-Telegram, 27 Apr. 2026
Ruby and sapphire mining began in the area in 1870, once rubies were discovered in the corundum mines.
—Trudy Haywood Saunders, Travel + Leisure, 27 Jan. 2026
Pure corundum is colorless, but trace elements like iron, titanium, chromium, gallium and vanadium give it colors like blue, yellow, red, green, pink, or purple.
—David Bressan, Forbes.com, 26 June 2025
The chromium replaces about 1% of the aluminum in the corundum or beryl crystal when a ruby or emerald forms underground at a high temperature and pressure.
—Daniel Freedman, The Conversation, 4 Feb. 2025
The domed disc is a pink synthetic corundum in the same vein as ruby or sapphire, and the result is a soft, translucent pink that shifts not only depending on viewing angle and lighting.
—Blake Buettner, Robb Report, 8 May 2024
At $950, the luxury wearable is made from black synthetic corundum with 18-karat yellow gold braided torchon detailing and a signature interlocking G logo.
—Sara Klausing, Men's Health, 4 Nov. 2022
Cite this Entry
“Corundum.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/corundum. Accessed 1 May. 2026.
Copy CitationKids Definition
corundum
noun
co·run·dum
kə-ˈrən-dəm
: a very hard mineral of aluminum oxide used for grinding, smoothing, or polishing or in some crystalline forms as a gem (as ruby or sapphire)
Medical Definition
corundum
noun
co·run·dum
kə-ˈrən-dəm
: a very hard mineral Al2O3 that consists of alumina occurring in massive form and as variously colored crystals which include the ruby and sapphire
Love words? Need even more definitions?
Merriam-Webster unabridged
