metamorphic
Gneiss
Foliated Metamorphic Rock
AI-generated identification · may be incorrectHardness of 6-7 on Mohs scale, distinct alternating light and dark compositional bands, vitreous to dull luster, granular to crystalline texture.
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Physical properties
Hardness of 6-7 on Mohs scale, distinct alternating light and dark compositional bands, vitreous to dull luster, granular to crystalline texture.
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
Used primarily as crushed stone for construction, road building, landscaping, and occasionally as dimension stone for architectural facing.
Geological facts
Gneiss contains some of the oldest known rocks on Earth, with certain formations dating back over 4 billion years.
Field identification & locations
Easily identified by its characteristic banded appearance known as gneissic banding; found globally in ancient shield areas and core mountain ranges.
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