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

It’s also a bonza industrial abrasive, and clear slices of synthetic corundum are used to make bullet-proof “glass.”

From Scientific American • Apr. 14, 2012

On the Mohs scale, which measures minerals’ hardness from 1 to 10, corundum ranks at 9.

From BusinessWeek • May 31, 2011

The hardness of emery is about 8, whereas that of pure corundum is 9.

From Encyclopaedia Britannica, 11th Edition, Volume 9, Slice 3 "Electrostatics" to "Engis" by Various