Quartz monzonite

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Quarry for the Salt Lake Temple. The ground is strewn with boulders and detached masses, which have fallen from the walls of Little Cottonwood Canyon. The quarrying consists of splitting up the blocks

Quartz monzonite (or adamellite) is an intrusive 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 whereas 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 LDS Church's Salt Lake Temple and the facade of the nearby LDS Conference Center. The blocks used in both were quarried in nearby Little Cottonwood Canyon, where the LDS Church's Granite Mountain vault is also located.