Porphyry

Not a root name, but a texturally-based name for any rock with coarse phenocrysts in a finer groundmass. Most commonly used for felsic rocks such as rhyolites, granites, etc.

An igneous rock of any composition that contains conspicuous phenocrysts in a fine-grained groundmass; a porphyritic igneous rock. The term (from the Ancient Greek word πορφύρα (porphyra) for the colour purple and 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 commonly precedes the term; e.g., diorite porphyry, although the reverse is better, e.g. porphyritic diorite. In many cases the main phenocryst minerals precedes the name, e.g. quartz porphyry or quartz-feldspar porphyry, where the classification is uncertain.