a kind of plagioclase feldspar occurring commonly in white crystals, sometimes shaded with gray, green, or red.
Origin of oligoclase
First recorded in 1825–35; oligo-
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for oligoclase
Historical Examples of oligoclase
At Danbury the mineral occurs with microcline and oligoclase embedded in dolomite.
Amelia Court House, Virginia, is another locality whence come pieces either of orthoclase or oligoclase exhibiting this property.
The felspar ranges from bytownite to oligoclase, being usually a variety of labradorite; orthoclase is scarce.
The felspar of the granulites is mostly orthoclase or cryptoperthite; microcline, oligoclase and albite are also common.
These intermediate members are the lime-soda felspars known as oligoclase, andesine, labradorite and bytownite.
British Dictionary definitions for oligoclase
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
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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.
The American Heritage® Science Dictionary
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