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An igneous rock consisting almost entirely of plagioclase feldspar, especially the labradorite variety.

[French anorthose, a kind of feldspar (Greek an-, not; see a-1 + Greek orthos, straight) + -ite.]

an·or′tho·sit′ic (-sĭt′ĭk) adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Geological Science) a coarse-grained plutonic igneous rock consisting almost entirely of plagioclase feldspar
[C19: from French anorthose (see an-, ortho-) + -ite1]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ænˈɔr θəˌsaɪt)

a granular plutonic rock composed largely of labradorite or a more calcic feldspar.
[1860–65; < French anorthose (an- an-1 + Greek orthós straight) + -ite1]
an•or`tho•sit′ic (-ˈsɪt ɪk) adj.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
References in periodicals archive ?
GreenSpar is a form of the mineral Anorthosite (aluminosilicate), a rare compositional variety of plagioclase feldspar.
The "Genesis Rock," a 4.4 billion-year-old anorthosite sample approximately 2 inches in length, brought back by Apollo 15 and used to determine the moon was formed by a giant impact, is lit inside a pressurized nitrogen-filled examination case in the lunar lab at the NASA Johnson Space Center Monday, June 17, 2019, in Houston.
Among them were green, yellow, and orange volcanic beads; black basalts from the dark maria regions; twisted breccias cemented together by meteorite impacts; and a light-toned rock called anorthosite.
Christie's auction offered an Egyptian fossil limestone jar, from the first and second dynasties, dating back to 3000-2650 BC, as well as an Egyptian anorthosite gneiss bowel, from the first and second dynasties, dating back to 3000 -- 2650BC.
and Zhou, W.G.: 2002, The experimental studies on electrical conductivities and P-wave velocities of anorthosite at high pressure and high temperature.
Govindaraju, "Report (1980) on three GIT-IWG rock reference samples: anorthosite from Greenland, AN-G; basalte d' Essey-la-Cote, BE-N; granite de Beauvoir, MAN," Geostandards Newsletter, vol.
B = Bamble lithotectonic domain; K = Kongsberg-Modum lithotectonic domain; RAC = Rogaland Anorthosite Complex; KPFZ = Kristiansand-Porsgrunn Fault Zone; KSFZ = Kongsberg- Sokna Fault Zone; MZ = Mylonite Zone; DBT = Dalsland Boundary Thrust; GZ = GotaelvZone; SFCZ = Sveconorwegian Frontal Deformation Zone; and LLDZ = Linkoping-Lofthammer Deformation Zone.
Normally, ilmenite is found in large quantities in the anorthosite or norite rocks.