metamorphic
Gneiss
Gneiss
AI-generated identification · may be incorrectHardness of 6-7 on the Mohs scale, characterized by distinct alternating light and dark compositional bands (gneissic banding). Exhibits a vitreous to dull luster and a foliated crystalline structure.
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Physical properties
Hardness of 6-7 on the Mohs scale, characterized by distinct alternating light and dark compositional bands (gneissic banding). Exhibits a vitreous to dull luster and a foliated crystalline structure.
Formation & geological history
Formed by high-temperature and high-pressure regional metamorphism of pre-existing igneous or sedimentary rocks deep within the Earth's crust.
Uses & applications
Commonly used as crushed stone for building construction, road aggregates, and occasionally as dimension stone for facing or landscaping.
Geological facts
Gneiss contains some of the oldest known rock material on Earth, with certain zircons found within it dating back over 4 billion years.
Field identification & locations
Easily identified in the field by its striking zebra-like banding of light quartz-feldspar and dark biotite-amphibole layers. Found globally in ancient continental shields.
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