Quartz monzonite or adamellite 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.
Quartz monzonite bedrock from a USGS drill core at Western Cape Cod, Massachusetts
Quartz monzonite extracted from a quarry in Little Cottonwood Canyon was used to build several buildings in Salt Lake City, Utah, including the The Church of Jesus Christ of Latter-day Saints' Salt Lake Temple, Church Administration Building, and Conference Center, as well as the Utah State Capitol.
The large boulders of Joshua Tree National Park in southern California are quartz monzonite.
- Media related to Quartz monzonite at Wikimedia Commons