Definition of plagioclase in English:

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plagioclase

Pronunciation: /ˈplājēəˌklās/
(also plagioclase feldspar)

noun

A form of feldspar consisting of aluminosilicates of sodium and/or calcium, common in igneous rocks and typically white.
Example sentences
  • Aligned igneous minerals of euhedral potassium feldspar, plagioclase, biotite and hornblende in an undeformed quartz matrix define a magmatic foliation.
  • All monazite grains are located in the rock matrix, which consists of quartz, muscovite, biotite, epidote, chlorite, plagioclase, potassium feldspar and garnet with a granoblastic texture.
  • Coexisting MI phases in these rocks include garnet, plagioclase, quartz, tourmaline and fluorite.

Origin

Mid 19th century: from plagio- + Greek klasis 'cleavage' (because originally characterized as having two cleavages at an oblique angle).

For editors and proofreaders

Syllabification: pla·gi·o·clase

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