orthoclase

[ awr-thuh-kleys, -kleyz ]

noun

1. a common white or pink mineral of the feldspar group, KAlSi 3 O 8 , having two good cleavages at right angles, and found in silica-rich igneous rocks: used in the manufacture of porcelain.

orthoclase

/ ˈɔːθəʊˌkleɪs; -ˌkleɪz /

noun

1. 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

orthoclase

/ ôr′thə-klās′ /

1. A white to yellowish red monoclinic mineral of the potassium feldspar group that forms from medium- to low-temperature magmas. Chemical formula: KAlSi 3 O 8 .

Word History and Origins

Origin of orthoclase¹

1840–50; ortho- + -clase < Greek klásis cleavage, breaking

Example Sentences

A transparent or translucent variety of common feldspar, or orthoclase, which often shows pearly opalescent reflections; - called by lapidaries moonstone.

From Project Gutenberg

Examples of substances exhibiting these three kinds of dispersion are borax, orthoclase and gypsum respectively.

From Project Gutenberg

Felspar if present may be orthoclase and oligoclase.

From Project Gutenberg

These larger felspars have no crystalline outlines and consist of orthoclase or microcline surrounded by borders of white oligoclase.

From Project Gutenberg

Of their minerals felspar Is usually the most abundant, and is principally labradorite and bytownite, though anorthite occurs in some, while oligoclase and orthoclase have been found in others.

From Project Gutenberg