metamorphic
Gneiss
Gneiss
AI-generated identification · may be incorrectHardness 6-7 on the Mohs scale, characterized by distinct alternating light and dark compositional banding. It exhibits a foliated texture with medium to coarse-grained crystals and a vitreous to pearly luster.
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Physical properties
Hardness 6-7 on the Mohs scale, characterized by distinct alternating light and dark compositional banding. It exhibits a foliated texture with medium to coarse-grained crystals and a vitreous to pearly luster.
Formation & geological history
Formed through high-grade regional metamorphism of preexisting igneous or sedimentary rocks under extreme heat and pressure, typically during continental collisions.
Uses & applications
Used primarily in the construction industry as crushed stone for road bases, building facades, and dimension stone countertops.
Geological facts
Some of the oldest known rocks on Earth, dating back over 4 billion years, are classified as gneiss. The distinctive light and dark bands are known as gneissic banding.
Field identification & locations
Identify in the field by its prominent alternating light (quartz and feldspar) and dark (biotite and amphibole) mineral bands. Found worldwide in ancient shield areas and core mountain ranges.
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