metamorphic
Banded Gneiss
Gneiss
AI-generated identification · may be incorrectHardness of 6-7 on the Mohs scale, with a banded or foliated texture showing alternating light and dark mineral layers. It has a vitreous to dull luster and a crystalline structure.
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Physical properties
Hardness of 6-7 on the Mohs scale, with a banded or foliated texture showing alternating light and dark mineral layers. It has a vitreous to dull luster and a crystalline structure.
Formation & geological history
Formed through high-grade regional metamorphism of preexisting igneous or sedimentary rocks under extreme heat and pressure, typically during mountain-building events.
Uses & applications
Used primarily as crushed stone for road construction, building foundations, and dimension stone for landscaping or architectural facing.
Geological facts
Gneiss contains some of the oldest known rocks on Earth, with certain formations dating back over 4 billion years. The distinctive light and dark bands are known as gneissic banding.
Field identification & locations
Identify in the field by its distinct compositional banding of light-colored quartz and feldspar alternating with dark mafic minerals. Found worldwide in ancient shield areas and core mountain ranges.
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