any of the feldspar minerals varying in composition from acidic albite, NaAlSi3O8, to basic anorthite, CaAl2Si2O8, found in most igneous rocks: shows twinning striations on good cleavage surfaces.
- Also called soda-lime feldspar.
- pla·gi·o·clas·tic [pley-jee-uh-klas-tik], /ˌpleɪ dʒi əˈklæs tɪk/, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use plagioclase in a sentence
The rock—which also contains the plain-old mineral plagioclase—includes pink spinel, a prized jewel on Earth.Space Bling: From Diamond Planets to Crystal Oceans to Precious Moon Jewels | Alexa Valiente, Jaewon Kang | October 13, 2012 | THE DAILY BEAST
The felted or hyalopilitic texture is the most common, and plagioclase is the principal groundmass constituent.Mount Rainier | Various
There is also some variation in the amount of quartz present, and in the relative importance of the orthoclase and plagioclase.Mount Rainier | Various
Vogesites contain hornblende and orthoclase; spessartites, hornblende and plagioclase.
Minettes contain biotite and orthoclase; kersantites, biotite and plagioclase.
Essentially it is a crystalline-granular compound of plagioclase, generally Labradorite and diallage.Volcanoes: Past and Present | Edward Hull
British Dictionary definitions for plagioclase
a series of feldspar minerals consisting of a mixture of sodium and calcium aluminium silicates in triclinic crystalline form: includes albite, oligoclase, and labradorite
- plagioclastic (ˌpleɪdʒɪəʊˈklæstɪk), adjective
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 plagioclase
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)Si2O8.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.