Origin of plagioclase
Examples from the Web for plagioclase
Historical Examples of plagioclase
Sometimes 584 the striae on crystal-faces are due to repeated lamellar twinning, as in the plagioclase felspars.
Many dolerites are porphyritic and carry phenocrysts of olivine, augite and plagioclase felspar (or of one or more of these).
More rarely biotite and augite exhibit the same relations to the plagioclase.
The former consist mainly of plagioclase, leucite and augite, while the latter contain olivine in addition.
Their essential minerals are pyroxene, plagioclase and garnet: chemically they resemble the gabbros.