CHARNOCKITE
Charnockites are very high-grade metamorphic rocks that straddle the boundary between igneous & metamorphic. Many charnockites have been given metamorphic and igneous names. I get the impression that no one really fully understands charnockites. My understanding is that charnockites are dark-colored, very coarsely-crystalline, quartzo-feldspathic with pyroxene, and are very high-grade metamorphic rocks (or at the very least, intimately associated with very high-grade metamorphic terranes). Some charnockites have obvious foliation, while the foliation is extremely subtle in other samples. Foliation is best seen in the black pyroxene component. The feldspar component of charnockite characteristically “glimmers” when tilted in the light (see especially the large lower feldspar crystal on photo of “Verde Butterfly Granite” below).
Ubatuba Granite from near the town of Ubatuba in southeastern Brazil. This late Neoproterozoic to Cambrian (~650-500 million years) charnockite has large, dark-greenish feldspars, black pyroxene, and some quartz.
Verde Butterfly Granite - garnetiferous charnockite (a.k.a. hypersthene monzogranite) from the Precambrian of southeastern Brazil. It formed during the late Neoproterozoic to Cambrian (~650-500 million years ago). The rock is dominated by feldspar (greenish), pyroxene (black), quartz, and garnet (very deep red).
Seaweed Green Granite (a.k.a. Pocono Green Granite, Pine Green Granite) - a garnetiferous charnockite from the Precambrian of Orissa State, Eastern Ghats Orogenic Belt, eastern India. The very dark red garnet component of this rock is mostly mixed with black pyroxene patches. The black pyroxene areas are generally elongated, and aligned more or less parallel throughout the rock (foliated texture).
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 shows 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.