Nara Brown Granite (a.k.a. Nara Granite, Caledonia Granite, Caledonia Nara Brown Granite, Caledonia Nara Granite) - this has the appearance of an ordinary porphyritic granite with K-feldspar phenocrysts, but petrologic and regional geologic work show that it is a charnockite (a porphyritic farsundite or porphyritic quartz mangerite, to be more specific).
Geologic Unit & Age: Rivière-à-Pierre Plutonic Suite, Grenville Orogeny metamorphism, late Mesoproterozoic, ~1.1 Ga.
Locality: quarry north of town of Rivière-à-Pierre, Portneuf County, southern Quebec, southeastern Canada.
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Charnockites are intrusive igneous rocks that are dark-colored and coarsely-crystalline. Mineralogically, charnockites have quartz, feldspar, and pyroxene. Many charnockites have been metamorphosed, sometimes with obvious foliation, but often with extremely subtle foliation, best seen in the black pyroxene component. The feldspar component of charnockite can “glimmer” when tilted in the light.
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