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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.


(Geological Science) a coarse-grained plutonic igneous rock consisting almost entirely of plagioclase feldspar
[C19: from French anorthose (see an-, ortho-) + -ite1]


(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.
References in periodicals archive ?
Indeed, all powdery ejecta, be they from anorthosite or basaltic rocks, are at least initially bright for this reason.
Forest Service's local station, the project includes mining 150,000 tons per year of anorthosite ore, a rock mineral that is used to bind concrete for building.
1999, Paleomagnetism, anisotropy of magnetic susceptibility, and argon-argon geochronology of the Clearwater anorthosite, Saskatchewan, Canada: Tectonophysics, v.
Rock types sampled in the Duck Lake Pluton include gabbro, orthopyroxene gabbro, gabbronorite, olivine gabbronorite, anorthosite, dunite, and wehrlite (Grammatikopoulos 1992; White 1996).
It rests on a footwall of anorthosite (consisting of calcium-and aluminium-rich silicate minerals).
A more serious piece of evidence against the existence of the Procellarum basin is the presence of anorthosite lying within the inner basin rim.
As revealed by the drill core, the complex consists of interlayered coarse-grained anorthosite and gabbro, both intruded by abundant finer grained gabbroic dykes.
The highlands are bright because they are largely made of a light-colored, aluminum-rich mineral called anorthosite.
The arc, which comprises a suite of calc-alkaline and A-type volcanic and plutonic rocks, along with coeval back-arc mafic dyke swarms, anorthosite complexes and elastic sedimentary deposits, extends along the Laurentian margin for over 5000 km of strike length.
This age is similar to that of the pegmatites in the underlying anorthosite.
Remarkably, this peak is the only known occurrence of anorthosite in the northwestern quadrant of the Moon.