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[per-i-kleys, -kleyz] /ˈpɛr ɪˌkleɪs, -ˌkleɪz/
a cubic mineral, native magnesia, MgO, occurring usually in metamorphosed dolomite.
1835-45; < German Periklas < New Latin periclasia, equivalent to peri- peri- + Greek klás(is) a breaking (cf. -clase) + -ia -ia Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for periclase


a mineral consisting of magnesium oxide in the form of isometric crystals or grains: occurs in metamorphosed limestone
Derived Forms
periclastic (ˌpɛrɪˈklæstɪk) adjective
Word Origin
C19: from New Latin periclasia, from Greek peri very + klasis a breaking, referring to its perfect cleavage
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Article for periclase

magnesium oxide mineral (MgO) that occurs as colourless to grayish, glassy, rounded grains in marble and in some dolomitic limestones, where it formed by the metamorphosis of dolomite at high temperatures. Rocks containing periclase have been identified at Monte Somma and Predazzo, Italy; Nordmark and Langban, Swed.; and Crestmore, Calif. Periclase may be a major component of the mantle of the Earth. For detailed physical properties, see oxide mineral (table)

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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