Quartz monzonite

Quartz monzonite is an intrusive, felsic, igneous rock that has an approximately equal proportion of orthoclase and plagioclase feldspars. It is typically a light colored phaneritic (coarse-grained) to porphyritic granitic rock. The plagioclase is typically intermediate to sodic in composition, andesine to oligoclase. Quartz is present in significant amounts. Biotite and/or hornblende constitute the dark minerals. Because of its coloring, it is often confused with granite, but whereas granite contains more than 20% quartz, quartz monzonite is only 5–20% quartz. Rock with less than five percent quartz is classified as monzonite. A rock with more alkali feldspar is a syenite whereas one with more plagioclase is a quartz diorite. The fine grained volcanic rock equivalent of quartz monzonite is quartz latite.

The term adamellite was originally applied by A. Cathrein in 1890 to orthoclase-bearing tonalite (likely a granodiorite) at Monte Adamello, Italy, in 1890, but later came to refer to quartz monzonite. The term is now deprecated.

Quartz monzonite porphyry is often associated with copper mineralization in the porphyry copper ore deposits.