Common in intrusive magmatic settings (Alpine and South American examples), it is composed of quartz, potassium feldspar, plagioclase, and mica, with large phenocrysts (often feldspar) embedded in a finer matrix, resulting from two crystallization phases at different depths and cooling rates. It is frequently associated with copper-molybdenum hydrothermal deposits (“porphyry deposits”).

Used as an ornamental and building stone for its mottled appearance and durability; of great economic and geological interest as the host rock for major global mineral deposits (copper, gold, molybdenum).