Monzonite(redirected from monzonites)
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(named after the city of Monzoni, Italy, in the Tirol), crystalline igneous rock consisting of approximately equal amounts of common potash feldspar and lime-soda feldspar (orthoclase and labradorite) and of a ferromagnesian mineral, usually pyroxene. In more acid varieties of monzonite a small amount of quartz may also be present; in more basic kinds there may be olivine. Chemically the group of monzonite rocks occupies an intermediate position between gabbros and syenites (average silica content of 55–65 percent); therefore monzonites are also called gabbro-syenites. Monzonite is a dense large-grained rock that is attractive when polished. It is used as a building material. Monzonites occur in many regions of the USSR—for example, the Ukraine and the Baikal region; abroad they are found in Italy, Norway, and other countries.