metamorphic
Gneiss
Gneiss
AI-generated identification · may be incorrectHardness 6-7 on Mohs scale, typically displays distinct light and dark compositional banding (gneissic banding), vitreous to dull luster, and granular texture.
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Physical properties
Hardness 6-7 on Mohs scale, typically displays distinct light and dark compositional banding (gneissic banding), vitreous to dull luster, and granular texture.
Formation & geological history
Formed through high-grade regional metamorphism of pre-existing igneous or sedimentary rocks under intense heat and directional pressure.
Uses & applications
Commonly used in the construction industry as crushed stone for road bases, building facades, and dimension stone.
Geological facts
Gneiss can contain some of the oldest known mineral grains on Earth, dating back over 4 billion years.
Field identification & locations
Easily identified in the field by its characteristic alternating bands of light-colored quartz/feldspar and dark-colored biotite/amphibole minerals.
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