metamorphic
Gneiss
Gneiss
AI-generated identification · may be incorrectHardness of 6-7 on the Mohs scale, characterized by distinct alternating light and dark compositional banding. It exhibits a foliated structure, vitreous luster, and variable specific gravity around 2.6-2.9.
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Physical properties
Hardness of 6-7 on the Mohs scale, characterized by distinct alternating light and dark compositional banding. It exhibits a foliated structure, vitreous luster, and variable specific gravity around 2.6-2.9.
Formation & geological history
Formed through high-grade regional metamorphism of pre-existing igneous or sedimentary rocks under intense heat and directional pressure, typically occurring deep within the Earth's crust during continental collisions.
Uses & applications
Used primarily in the construction industry as crushed stone for road base, building facades, and dimension stone for landscaping.
Geological facts
Gneiss is one of the oldest rock types on Earth, with some specimens dating back over 4 billion years. The banded patterns are often called gneissic banding.
Field identification & locations
Identified easily in the field by its alternating light (quartz and feldspar) and dark (biotite and amphibole) mineral bands. Commonly found in ancient continental shields and core mountain ranges.
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