metamorphic

Banded gneiss

Gneiss, chiefly quartz–feldspar–mica

AI-generated identification · may be incorrect

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.

Identified August 28, 2026More metamorphic →

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Physical properties

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.