One of the mysteries of the English language finally explained.
Extremely hard aluminum oxide, used as an abrasive. Ruby and sapphire are varieties of corundum.
- ‘Red gem-quality corundum is known as ruby; all other colors of gem corundum are referred to as sapphire, with a prefix denoting the color of the stone.’
- ‘Several Colorado gem minerals (lazurite and the state's minor occurrences of corundum and cordierite) form in metamorphic rocks.’
- ‘Diamond has been assigned a hardness value of 10, only a single point higher than corundum on Mohs scale, although it is far harder than this would indicate.’
- ‘First, to prove beryllium could diffuse into corundum and create a color change, he heated pink sapphires with beryllium and got yellow rims.’
- ‘In 1995 field reconnaissance in the central Laramie Range of southeastern Wyoming led to the discovery of a new source of gem- and near-gem-quality cordierite and corundum.’
- ‘One of these occurs at Baggot's Rock, where specks of corundum are found.’
- ‘In summary, the presence of additional occurrences of gem-quality corundum and cordierite in Wyoming needs to be seriously considered’
- ‘This is, of course, ludicrous because corundum and quartz are mutually exclusive.’
- ‘Also on a hillside to the north is a contact metamorphosed bed rich in small, dark blue, platy corundum crystals.’
- ‘Reports of gem-quality corundum are rare in Wyoming, although both ruby and sapphire have been noted.’
- ‘Chapters 2-19 describe eighteen specific traditional gemstones or families, beginning with corundum and ending with rhodonite.’
- ‘All granites are peraluminous as implied by the ubiquity of normative corundum.’
- ‘In the 1980s, geologists in Moscow found several small diamonds and minerals, such as zircon, garnet, and corundum, in the alluvia of the River Karla.’
- ‘Sapphire comes in every color (except red, because red corundum is called ruby) and is one of the hardest/most durable gems next to diamond.’
- ‘The grayish-blue, partly gemmy cordierite, when first discovered in the early twentieth century, was mistakenly reported as corundum.’
- ‘He also found particles of gemstones such as corundum, garnet, rutile, and argentite.’
- ‘Although blue corundum, zircon, and tourmaline occur in Colorado, they are not known to produce gems.’
Early 18th century: from Tamil kuruntam and Telugu kuruvindam.
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