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

Rubies and sapphires, which are both made of the same mineral, corundum, are “quite durable,” according to John Watkins, an independent goldsmith in Lake Nacimiento, California.

From BusinessWeek • May 31, 2011

Thus, corundum when pure is colourless, but the presence of traces of certain mineral substances imparts to it not only the red of ruby and the blue of sapphire, but almost every other colour.

From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 5 "Gassendi, Pierre" to "Geocentric" by Various