metamorphic
Gneiss
Orthogneiss / Paragneiss
AI-generated identification · may be incorrectHardness 6-7 on Mohs scale, characterized by distinct alternating light and dark compositional banding. It possesses a foliated structure and vitreous luster with a specific gravity around 2.6-2.9.
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Physical properties
Hardness 6-7 on Mohs scale, characterized by distinct alternating light and dark compositional banding. It possesses a foliated structure and vitreous luster with a specific gravity around 2.6-2.9.
Formation & geological history
Formed through high-grade regional metamorphism of pre-existing igneous or sedimentary rocks under extreme heat and pressure, typically during continental collisions.
Uses & applications
Used primarily as crushed stone for road construction, building facades, landscaping, and monumental stone.
Geological facts
Gneiss contains some of the oldest known rock material on Earth, with certain zircons found within gneiss dating back over 4 billion years.
Field identification & locations
Identify in the field by its striking zebra-like banding of light quartz/feldspar and dark biotite/amphibole minerals. Commonly found in ancient cratons and mountain cores worldwide.
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