Porphyritic adj. (Min.) Relating to, or resembling, porphyry, that is, characterized by the presence of distinct crystals, as of feldspar, quartz, or augite, in a relatively fine-grained base, often aphanitic or cryptocrystalline.
... compact, fine-grained amorphous sandstone, having an almost flinty fracture; this rock, in a few miles, gives place to granite and gneiss, frequently broken up by the upheaval of whinstone and porphyritic trap hills, having an elevation of from 100 to 500 feet above ... — Journals of Australian Explorations • A C and F T Gregory
... we rode along among porphyritic mountains, getting higher at every turn, and enjoying the clear bright air. Now and then we met or passed a long recua (train) of loaded mules, taking care to keep the safe side of the road till we were rid of them. It is not pleasant to ... — Anahuac • Edward Burnett Tylor
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