oligoclase

These intermediate members are the lime-soda felspars known as oligoclase, andesine, labradorite and bytownite.
Encyclopaedia Britannica, 11th Edition, Volume 10, Slice 2|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|Various
The felspar ranges from bytownite to oligoclase, being usually a variety of labradorite; orthoclase is scarce.
Encyclopaedia Britannica, 11th Edition, Volume 16, Slice 5|Various
At Danbury the mineral occurs with microcline and oligoclase embedded in dolomite.
Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 9|Various

Amelia Court House, Virginia, is another locality whence come pieces either of orthoclase or oligoclase exhibiting this property.
Birds and Nature, Vol. 12 No. 2 [July 1902]|Various

British Dictionary definitions for oligoclase

oligoclase

/ (ˈɒlɪɡəʊˌkleɪs) /

noun

a white, bluish, or reddish-yellow feldspar mineral of the plagioclase series, consisting of aluminium silicates of sodium and calcium. Formula: NaAlSi 3 O 8 .CaAl 2 Si 2 O 8

Word Origin for oligoclase

C19: from oligo- + -clase

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

Scientific definitions for oligoclase

oligoclase

[ ŏl′ĭ-gō-klās′, ō′lĭ- ]

A white to gray triclinic mineral of the plagioclase feldspar group. Oligoclase occurs in igneous rocks with a relatively high silica content, such as granite. Chemical formula: (Na,Ca)(Al,Si)AlSi2O8.