metamorphic

Banded gneiss

Gneiss, composed mainly of quartz, feldspar, and mica

AI-generated identification · may be incorrect

Gray, coarse-grained rock with faint light–dark banding and a dull to mildly vitreous luster. Quartz and feldspar are typically Mohs 6–7; mica produces planar foliation and occasional sparkle. Exact identification is limited because the specimen is weathered and partly out of focus.

Identified September 17, 2026More metamorphic →

Explore Banded gneiss in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms when granite or other rocks undergoes high-grade regional metamorphism, causing mineral segregation into bands; commonly Precambrian to Paleozoic in age. It occurs in ancient continental shields and high-grade metamorphic terrains.

Uses & applications

Used as dimension stone, paving, aggregate, and landscaping rock; attractive polished pieces are collected, though this example appears ordinary.

Geological facts

Gneissic banding records intense heat, pressure, and deformation rather than simple sedimentary layering. Some gneisses preserve relict igneous minerals or folded compositional bands.

Field identification & locations

Look for alternating quartz/feldspar-rich light bands and biotite/amphibole-rich dark bands, coarse grains, and strong foliation; it should not fizz with dilute acid. Common worldwide in Precambrian basement, including Canada, Scandinavia, India, Africa, and the Appalachians.