metamorphic

Banded gneiss

Foliated gneiss, likely quartz–feldspar–biotite gneiss

AI-generated identification · may be incorrect

Distinct alternating dark and light mineral bands, with coarse, uneven texture and mica-rich layers; likely Mohs hardness 6–7, vitreous to dull luster, and no true cleavage as a whole rock. The image suggests quartz and feldspar in pale bands and dark biotite or amphibole, but exact minerals cannot be confirmed visuall…

Identified October 13, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when pre-existing rock is recrystallized and segregated into bands under high heat and pressure, commonly during mountain-building; its age depends on the source rock and region.

Uses & applications

Used as building and decorative stone, paving, and landscaping material; attractive banded pieces are collected as specimens.

Geological facts

Gneissic banding reflects mineral separation during metamorphism and is not sedimentary layering.

Field identification & locations

Look for coarse, interlocking grains and irregular, alternating light and dark bands; common in ancient continental shields and mountain belts. Small hand specimens commonly sell for about $5–$30 USD, depending on size, appearance, and locality.