metamorphic
Gneiss
Metamorphic Gneiss
AI-generated identification · may be incorrectHardness of 6-7 on the Mohs scale, characterized by distinct alternating light and dark compositional banding (gneissic banding). Exhibits a vitreous to dull luster and a foliated texture.
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Physical properties
Hardness of 6-7 on the Mohs scale, characterized by distinct alternating light and dark compositional banding (gneissic banding). Exhibits a vitreous to dull luster and a foliated texture.
Formation & geological history
Formed by high-temperature and high-pressure metamorphic processes acting on pre-existing igneous or sedimentary rocks deep within the Earth's crust.
Uses & applications
Used primarily as crushed stone for building construction, road bases, and architectural dimension stone.
Geological facts
Gneiss contains some of the oldest known rocks on Earth, dating back over 4 billion years in places like the Acasta Gneiss in Canada.
Field identification & locations
Identified easily in the field by its characteristic zebra-like banding of light quartz/feldspar and dark biotite/amphibole minerals. Found globally in ancient shield regions.
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