metamorphic
Gneiss
Gneiss; a foliated metamorphic rock commonly composed of quartz, feldspar, and mica
AI-generated identification · may be incorrectCoarse-grained, pale gray to cream with darker mineral bands; typically hard (about 6–7 Mohs), with a granular texture and pronounced compositional banding. The image suggests gneiss, though individual minerals are not clearly resolved.
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Physical properties
Coarse-grained, pale gray to cream with darker mineral bands; typically hard (about 6–7 Mohs), with a granular texture and pronounced compositional banding. The image suggests gneiss, though individual minerals are not clearly resolved.
Formation & geological history
Forms when granite or other rocks undergo high-grade heat and pressure, often during mountain building; ages vary widely, commonly hundreds of millions to billions of years.
Uses & applications
Used as dimension stone, paving, landscaping aggregate, and decorative building stone; attractive pieces may be collected.
Geological facts
Gneissic banding reflects minerals segregated under intense metamorphism, rather than sedimentary layers.
Field identification & locations
Look for alternating light quartz/feldspar-rich and dark mica- or amphibole-rich bands; common in ancient continental basement and mountain belts worldwide. The image shows coarse, banded rock, but a closer view would help confirm identification.
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