oligoclase

[ ol-i-goh-kleys ]

noun

, Mineralogy.

1. a kind of plagioclase feldspar occurring commonly in white crystals, sometimes shaded with gray, green, or red.

oligoclase

/ ˈɒlɪɡəʊˌkleɪs /

noun

1. 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

oligoclase

/ ŏl′ĭ-gō-klās′,ō′lĭ- /

1. 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)AlSi 2 O 8 .

Word History and Origins

Origin of oligoclase¹

First recorded in 1825–35; oligo- + -clase

Word History and Origins

Origin of oligoclase¹

C19: from oligo- + -clase

Example Sentences

A variety of translucent quartz, spangled throughout with scales of yellow mica. ÷ feldspar, a variety of oligoclase with internal firelike reflections due to the presence of minute crystals, probably of hematite; sunstone.

From Project Gutenberg

Their felspar ranges from oligoclase to andesite and labradorite, and is often very zonal; sanidine occurs also in some dacites, and when abundant gives rise to rocks which form transitions to the rhyolites.

From Project Gutenberg

F� de Nuevo-Mexico, the Si�rra de San Francisco, west of the Rocky Mountains and Pueblo Zuni, consist of hornblende, oligoclase, and brown mica.

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