Porphyroid - definition of porphyroid by The Free Dictionary
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Metamorphic rock having porphyritic texture.
(Geological Science) (of metamorphic rocks) having a texture characterized by large crystals set in a finer groundmass
(Geological Science) a metamorphic rock having this texture
References in periodicals archive
The relict porphyroid
texture of the rock is caused by the presence of olivine coarse grains (separated by a fine grained mass composed of serpentine grains and ore mineral) fully substituted by serpentine.
They locally contain intercalations of crystalline limestones and dolomites (marbles), amphibolites, amphibole schists, quartzite and quartzite schists, graphite quartzites and mica schists, porphyroids
Fine flakes of muscovite (sericite) and chlorite are typical constituents of shales, slates, phyllites, porphyroids