corundum

Example Sentences

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Diamond defines a hardness of 10 and is actually about four times harder than corundum, which is 9.

From Textbooks • Jan. 1, 2017

The Bronco mane and eyeball were created from orange sapphires while the head features pave-set diamonds and custom-cut corundum blue stone.

From Washington Times • Jun. 12, 2016

This crystalline aluminum mineral is called corundum, and people have been wearing it with pride for thousands of years.

From Scientific American • Apr. 14, 2012

Diamonds are a 10 and almost four times harder than corundum.

From BusinessWeek • May 31, 2011

The mineral occurs as an alteration product of corundum or emery, and is found in granular limestone and other crystalline rocks.

From Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4 "Diameter" to "Dinarchus" by Various