A medium to coarse-ground intrusive rock containing less than 20% quartz.
an igneous rock composed of nearly equal amounts of plagioclase and orthclase containing sodium and other minerals, intermediate in composition between syenite and diorite. [AHDOS
Monzonite is an intermediate igneous intrusive rock composed of approximately equal amounts of sodic to intermediate plagioclase and orthoclase feldspars with minor amounts of hornblende, biotite and other minerals. Quartz a minor constituent or is absent; with greater than 10% quartz the rock is termed a quartz monzonite.