metamorphic
Banded gneiss
Gneiss, chiefly quartz–feldspar–mica
AI-generated identification · may be incorrectTypically gray, brown, and white with coarse alternating mineral bands; vitreous to dull luster, interlocking granular texture, no strong cleavage as a whole, and Mohs hardness about 6–7. The specimen appears quartz- and feldspar-rich with dark biotite or amphibole layers.
Identified More metamorphic →
Explore Banded gneiss in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Typically gray, brown, and white with coarse alternating mineral bands; vitreous to dull luster, interlocking granular texture, no strong cleavage as a whole, and Mohs hardness about 6–7. The specimen appears quartz- and feldspar-rich with dark biotite or amphibole layers.
Formation & geological history
Formed when granite or other felsic rock underwent intense regional metamorphism, producing compositional banding; commonly Precambrian to younger in age. Exact identification and age require microscopy or chemical testing.
Uses & applications
Used as building stone, paving, aggregate, and architectural dimension stone; attractive polished pieces are collected but rarely gem-quality.
Geological facts
Gneissic banding reflects mineral segregation during high heat and pressure, not ordinary sedimentary layering.
Field identification & locations
Identify it by coarse, strongly contrasting light and dark bands, harder quartz grains, and a massive, crystalline texture; common in ancient continental shields and high-grade metamorphic terrains. The image could also represent banded granite or migmatite, so a fresh surface and hand lens would help.
More like this
