Porphyry

Porphyry (Greek porphyros, “purple”), term originally applied to an Egyptian rock composed of prominent crystals of feldspar embedded in a red or purple matrix, but now applied to any igneous rock having well-defined crystals embedded in a mass of relatively finer grained material. The fine-grained matrix is called the groundmass and the larger crystals, phenocrysts. Igneous rocks of any mineral composition may have porphyritic varieties. The substance known as porphyry copper consists of copper minerals distributed in a body of porphyry.