metamorphic
Gneiss
Orthogneiss / Paragneiss
AI-generated identification · may be incorrectHardness 6-7 on Mohs scale, foliated texture with distinct alternating light and dark compositional bands, vitreous to dull luster, specific gravity 2.6-3.0.
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Physical properties
Hardness 6-7 on Mohs scale, foliated texture with distinct alternating light and dark compositional bands, vitreous to dull luster, specific gravity 2.6-3.0.
Formation & geological history
Formed by high-grade regional metamorphism of preexisting igneous or sedimentary rocks under intense heat and directed pressure, typically during mountain-building events.
Uses & applications
Used primarily in the construction industry as crushed stone for road bases, building facades, and decorative landscaping blocks.
Geological facts
Gneiss contains some of the oldest known rock fragments on Earth, with certain zircons dated back over 4 billion years. The region near 47.8°N, 9.6°E (Alpine foothills) frequently features metamorphic erratics.
Field identification & locations
Identified in the field by its striking zebra-like banding of light quartz-feldspar layers and dark biotite-amphibole layers.
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