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- Igneous rock containing conspicuous pheocrysts in
fine-grained or glassy
groundmass.
Source: Leet, L. Don. 1982.
Physical Geology, 6th Edition. Englewood Cliffs, NJ: Prentice-Hall
- An igneous rock of any composition that contains conspicuous phenocrysts
in a fine-grained groundmass; a porphyritic igneous rock. The term (from a
Greek word for a purple dye) was first applied to a purple-red rock
quarried in Egypt and characterized by phenocrysts of alkali feldspar. The
rock name descriptive of the groundmass composition usually precedes the
term; e.g., diorite porphyry. Obsolete syn: porphyrite. AGI
Source:
Dictionary of Mining, Mineral, and Related Terms
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