metamorphic
Weathered banded metamorphic rock, likely gneiss
Banded gneiss; commonly quartz–feldspar–mica assemblage
AI-generated identification · may be incorrectTypically Mohs 6–7, with gray, tan, and rusty weathered bands, vitreous to dull luster, and coarse recrystallized grains; foliation produces planar layering but usually no strong cleavage. The image suggests quartz, feldspar, mica, and iron-oxide staining.
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Physical properties
Typically Mohs 6–7, with gray, tan, and rusty weathered bands, vitreous to dull luster, and coarse recrystallized grains; foliation produces planar layering but usually no strong cleavage. The image suggests quartz, feldspar, mica, and iron-oxide staining.
Formation & geological history
Formed when preexisting igneous or sedimentary rock underwent high-grade heat and pressure, producing compositional banding and recrystallization; ages commonly range from Precambrian to Paleozoic. Exact identification requires a fresh surface or thin section.
Uses & applications
Used as crushed aggregate, dimension stone, landscaping rock, and occasionally as decorative slabs; generally has little gemstone value.
Geological facts
Gneissic banding reflects mineral segregation during metamorphism rather than ordinary sedimentary layering. Weathering commonly concentrates orange-brown iron oxides along fractures and foliation.
Field identification & locations
Look for alternating light quartz/feldspar-rich and dark mica/amphibole-rich bands, visible interlocking grains, and a hard, resistant texture. Common in continental shield regions and mountain belts worldwide; a streak, fresh break, and hand lens help distinguish it from weathered granite or schist.
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