Quartz monzonite

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Quartz monzonite is a felsic igneous rock that has an approximately equal proportion of orthoclase and plagioclase feldspars. 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. Quartz monzonite porphyry is often associated with copper mineralization in the porphyry copper ore deposits. Because of its coloring it is often confused with granite, but wheras the mass of granite is 20% quartz, quartz monzonite is only 5-20% quartz.

A massive outcrop of this igneous rock can be seen on the bald summit of Croydon Mountain in New Hampshire, USA. It is also the material used to construct the Mormon Salt Lake Temple and the facade of the nearby LDS Conference Center. The blocks used in both were quarried in nearby Little Cottonwood Canyon.