orthoclasen.
/ˈɔːθə(ʊ)kleɪz/, /ˈɔːθə(ʊ)kleɪs/, U.S. /ˈɔrθəˌkleɪs/, /ˈɔrθəˌkleɪz/ Mineralogy.
A potassium-rich alkali feldspar which occurs widely in rocks and as free crystals, typically white or pink. Also more fully orthoclase feldspar.Pure orthoclase has the formula KAlSi3O8. Crystal system: monoclinic.
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the world > the earth > minerals > types of mineral > silicates > tectosilicate > [noun] > feldspar > orthoclase
orthose1814
orthoclase1831
potash feldspar1845
potassium feldspar1894
1831 Edinb. New Philos. Jrnl. 11 388 Hardness equal that of orthoclase felspar.
1839 Jrnl. Franklin Inst. 24 219 Adularia or orthoclase.
1849 J. Nicol Man. Mineral. 119 All orthoclase from trachyte contains soda along with the potash.
1863 S. R. Graves Yachting Cruise Baltic 142 The felspar of this quarry is of two kinds, orthoclase and oligoclase, in large masses, the former pink, and the latter quite white.
1900 Sillman Mineral. 87 Ground orthoclase is extensively used as a glaze.
1933 Ecology 14 391 According to Paige..the reddish tone of the granite is largely due to potash feldspars in the form of microcline, orthoclase, and albite-oligoclase.
1955 Sci. Amer. Apr. 79/1 Granite is made up of three principal minerals: quartz (SiO2), albite feldspar (NaAlSi308), and orthoclase feldspar (KAlSi308).
1990 C. Pellant Rocks, Minerals & Fossils 13 Luxullianite. Tourmaline is a common accessory in many granites and in this rock pink orthoclase has much altered margins surrounded by black tourmaline and some grey quartz.
Compounds
General attributive with the sense ‘consisting of or containing orthoclase’, as orthoclase crystal, orthoclase group, etc.
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the world > the earth > minerals > mineral sources > [adjective] > yielding a mineral or metal > others
amethystine1670
marcasitical1670
cawky1676
blendy1683
sylvanitic1796
ytter1805
phosphatic1818
pyroxenic1819
hornblendic1823
muriatiferous1823
platiniferous1828
quartziferous1831
hypersthenic1838
schorly1838
uralitic1845
blendous1847
rutilated1849
orthoclase1853
palladiferous1866
peridotic1867
paragonitic1868
vivianitized1870
andesitic1876
tremolitic1880
phosphoriferous1881
kaolinitic1885
saussuritic1885
perthitic1887
strontianiferous1888
radiferous1899
myrmekitic1916
montmorillonitic1939
illitic1949
the world > the earth > minerals > types of mineral > silicates > tectosilicate > [adjective] > feldspar > varieties of feldspar
orthoclase1853
andesitic1876
saussuritic1885
perthitic1887
myrmekitic1916
1853 Sci. Mem.: Nat. Hist. 41 A granular whitish gray trachyte, containing hornblende and orthoclase crystals.
1865 W. S. O. tr. L. Figuier World before Deluge 58 Alongside these orthoclase crystals, quartz is frequently implanted.
1867 R. I. Murchison Siluria (new ed.) i. 11 Four separate stages of orthoclase-gneiss.
1940 F. F. Grout Kemp's Handbk. Rocks (ed. 6) i. 11 They [sc. the feldspars] are divided for hand specimen study into two groups, the orthoclase group (including microcline) and the plagioclase group from albite to anorthite.
1993 Jrnl. Petrol. 34 433 Recrystallization of the initial single-phase mesoperthite feldspar into separate orthoclase and oligoclase grains.
This entry has been updated (OED Third Edition, September 2004; most recently modified version published online March 2022).
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n.1831