[ awr-thuh-kleys, -kleyz ]
/ ˈɔr θəˌkleɪs, -ˌkleɪz /


a common white or pink mineral of the feldspar group, KAlSi3O8, having two good cleavages at right angles, and found in silica-rich igneous rocks: used in the manufacture of porcelain.

Origin of orthoclase

1840–50; ortho- + -clase < Greek klásis cleavage, breaking
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for orthoclase

British Dictionary definitions for orthoclase

/ (ˈɔːθəʊˌkleɪs, -ˌkleɪz) /


a white to pale yellow, red, or green mineral of the feldspar group, found in igneous, sedimentary, and metamorphic rocks. It is used in the manufacture of glass and ceramics. Composition: potassium aluminium silicate. Formula: KAlSi 3 O 8 . Crystal structure: monoclinic
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Science definitions for orthoclase

[ ôrthə-klās′ ]

A white to yellowish red monoclinic mineral of the potassium feldspar group that forms from medium- to low-temperature magmas. Chemical formula: KAlSi3O8.
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