Affixes

Porphyry is a hard igneous rock containing crystals of feldspar in a fine-grained, typically reddish groundmass; its name derives from Greek porphura, purple. Examples of the form include lamprophyre (Greek lampros, bright, shining), a porphyritic igneous rock with phenocrysts chiefly of biotite; granophyre, a granitic rock in which feldspar and quartz are intergrown; vitrophyre, any of a class of porphyritic rocks characterized by an igneous texture in which phenocrysts are embedded in a glassy groundmass.