plagioclase

[ pley-jee-uh-kleys ]

noun

1. any of the feldspar minerals varying in composition from acidic albite, NaAlSi 3 O 8 , to basic anorthite, CaAl 2 Si 2 O 8 , found in most igneous rocks: shows twinning striations on good cleavage surfaces.

plagioclase

/ ˈpleɪdʒɪəʊˌkleɪz; ˌpleɪdʒɪəʊˈklæstɪk /

noun

1. a series of feldspar minerals consisting of a mixture of sodium and calcium aluminium silicates in triclinic crystalline form: includes albite, oligoclase, and labradorite

plagioclase

/ plā′jē-ə-klās′ /

1. Any of a series of common feldspar minerals, consisting of differing mixtures of sodium and calcium aluminum silicates. Plagioclase is typically white, yellow, or reddish-gray, but it can also be blue to black. It occurs in igneous rocks. The minerals albite, oligoclase, andesine, labradorite, bytownite, and anorthite are all plagioclases. Chemical formula: (Na,Ca)Al(Si,Al)Si 2 O 8 .

Derived Forms

• plagioclastic, adjective

Other Words From

• pla·gi·o·clas·tic [pley-jee-, uh, -, klas, -tik], adjective

Word History and Origins

Origin of plagioclase¹

First recorded in 1865–70; plagio- + -clase

Example Sentences

The rock—which also contains the plain-old mineral plagioclase—includes pink spinel, a prized jewel on Earth.

From The Daily Beast

The felted or hyalopilitic texture is the most common, and plagioclase is the principal groundmass constituent.

From Project Gutenberg

There is also some variation in the amount of quartz present, and in the relative importance of the orthoclase and plagioclase.

From Project Gutenberg

Vogesites contain hornblende and orthoclase; spessartites, hornblende and plagioclase.

From Project Gutenberg

Minettes contain biotite and orthoclase; kersantites, biotite and plagioclase.

From Project Gutenberg

Essentially it is a crystalline-granular compound of plagioclase, generally Labradorite and diallage.

From Project Gutenberg