• WordNet 3.6
    • n orthoclase a white or colored monoclinic feldspar
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Webster's Revised Unabridged Dictionary
    • n Orthoclase (Min) Common or potash feldspar crystallizing in the monoclinic system and having two cleavages at right angles to each other. See Feldspar.
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Century Dictionary and Cyclopedia
    • n orthoclase Common or potash feldspar, a silicate of aluminium and potassium, occurring in monoclinic crystals and also massive. It has two perfect cleavages, at right angles to each other (whence the name). It varies much in color, from white to yellow, red, and green. Adularia, including most moonstone, is a crystallized variety, transparent or nearly so, characteristic especially of the crystalline rocks of the Alps; valencianite, from Valenciana, Mexico, is similar to it. Sanidine is a glassy variety, usually containing more or less soda; it is characteristic of certain igneous rocks, as trachyte, phonolite, etc.; rhyacolite, from Monte Somma, Vesuvius, is similar. Loxoclase is a variety from Hammond, New York, and murchisonite one from Exeter, England, the latter showing golden-yellow reflections on a surface nearly parallel to the orthopinacoid. Orthoclase is an essential constituent of granite and some other crystalline rocks, and often occurs in large masses in granite-veins, and is then quarried and used in making pottery. Much of the potash feldspar called orthoclase is really the related triclinic species microcline. The name anorthoclase has been given to some kinds of triclinic feldspar containing considerable potash, which are more closely related to albite than to microcline in optical characters. See feldspar. Also called orthose.
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Chambers's Twentieth Century Dictionary
    • n Orthoclase or′tho-klāz common or potash feldspar
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Webster's Revised Unabridged Dictionary
Ortho-, + Gr. to break
Chambers's Twentieth Century Dictionary
Gr. orthos, straight, klasis, a fracture.


In literature:

In this way I have melted beryl, orthoclase, and quartz.
"Scientific American Supplement, Vol. XXI., No. 531, March 6, 1886" by Various
Granite containing orthoclase felspar produces a fairly fertile soil.
"Manures and the principles of manuring" by Charles Morton Aikman
Other kinds of felspar, even orthoclase, may however also show the aventurine appearance.
"Encyclopaedia Britannica, 11th Edition, Volume 3, Part 1, Slice 1" by Various
This curve would represent the conditions under which orthoclase is in equilibrium with the molten magma.
"The Phase Rule and Its Applications" by Alexander Findlay
In syenite and greenstone it occurs more commonly than orthoclase.
"Geology" by James Geikie
Among the applications of felspar is that of pure orthoclase in the manufacture of artificial teeth.
"Encyclopaedia Britannica, 11th Edition, Volume 10, Slice 2" by Various
The felspar of the granulites is mostly orthoclase or cryptoperthite; microcline, oligoclase and albite are also common.
"Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 3" by Various
Felspar if present may be orthoclase and oligoclase.
"Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 5" by Various
Examples of substances exhibiting these three kinds of dispersion are borax, orthoclase and gypsum respectively.
"Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7" by Various