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
The examples and perspective in this section deal primarily with United States and do not represent a worldwide view of the subject. (November 2019) (Learn how and when to remove this template message)
In the White Mountains and western highlands of New Hampshire, the Kinsman Quartz Monzonite is an extensive formation that underlies Kinsman Mountain, parts of Franconia Notch, Mount Cardigan, and Mount Sunapee.
Quartz monzonite extracted from a quarry in Little Cottonwood Canyon was used to build several buildings in Salt Lake City, Utah, including 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.
- Classification of Igneous Rocks Archived September 30, 2011, at the Wayback Machine
- Titley, Spencer R. and Carol L. Hicks, Geology of the Porphyry Copper Deposits, University of Arizona Press, 1966, p. 35
- Billings, M.P. (1956). "The Geology of New Hampshire: Part II - Bedrock Geology". ngmdb.usgs.gov. New Hampshire State Planning and Development Commission. Retrieved September 17, 2020.
- Idaho Batholith
- Media related to Quartz monzonite at Wikimedia Commons