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plagioclase Line breaks: plagio|clase
Pronunciation: /ˈpleɪdʒɪə(ʊ)kleɪz/
(also plagioclase feldspar)

Definition of plagioclase in English:


[mass 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.


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

Definition of plagioclase in:
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