charnockite

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charnockite A light-coloured, medium to coarse-grained igneous rock containing quartz and microcline feldspar (see ALKALI FELDSPAR) as major components with, in order of decreasing abundance, oligoclase feldspar (see PLAGIOCLASE FELDSPAR), hypersthene, biotite, and magnetite. Despite its low abundance, hypersthene (a calcium-poor, iron-rich pyroxene) is a distinctive feature of this rock. Rocks with a charnockite mineralogy can also be formed by the metamorphism of quartzo-feldspathic rock under dry granulite facies conditions. The type location for the rock is in Tamil Nadu (formerly Madras), India.

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