metamorphic
Banded Gneiss
Gneiss
AI-generated identification · may be incorrectHardness 6-7 on Mohs scale; distinctive alternating light and dark compositional bands; vitreous to dull luster; massive, foliated crystal structure.
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Physical properties
Hardness 6-7 on Mohs scale; distinctive alternating light and dark compositional bands; vitreous to dull luster; massive, foliated crystal structure.
Formation & geological history
Formed through high-grade regional metamorphism of pre-existing igneous or sedimentary rocks under intense heat and directional pressure, typically during mountain-building events.
Uses & applications
Used primarily as crushed stone for construction, road building, and as dimension stone for architectural facings and landscaping.
Geological facts
Gneiss contains some of the oldest known rock material on Earth, with certain zircons within gneiss dating back over 4 billion years.
Field identification & locations
Identify by its striking zebra-like banding of light quartz/feldspar and dark biotite/amphibole minerals; commonly found in ancient continental shields.
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