Orthogneiss, Bisti Badlands, New Mexico A gneiss with mineralogy and texture indicating derivation from a phaneritic igneous rock protolith.
Orthogneiss, Bisti Badlands, New Mexico A gneiss with mineralogy and texture indicating derivation from a phaneritic igneous rock protolith. Typically consists of abundant feldspar, with quartz, and variable hornblende, biotite, and muscovite, with a relatively homogeneous character. Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct cleavage. Gneisses are common in the ancient crust of continental shields. Some of the oldest rocks on Earth are gneisses, such as the Acasta Gneiss.
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Photo credit: © Phil Degginger / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: activity, banding, biotite, building, composition, continental, crust, crustal, deformation, facies, feldspar, foliated, foliation, formation, geological, geology, gneiss, gneissic, granite, granitic, high-grade, igneous, mapping, metamorphic, metamorphism, mineral, mineralogy, mountain, orthogneiss, petrology, processes, protolith, quartz, regional, rock, rocks, specimen, specimens, structural, tectonic, texture, transformation
