metamorphic

Banded gneiss pebble

Gneiss, commonly quartz–feldspar–mica gneiss

AI-generated identification · may be incorrect

Typically 6–7 Mohs; gray, cream, and dark bands with a granular texture and dull to slightly glassy luster. Composed mainly of quartz and feldspar with biotite or hornblende; the banding reflects mineral segregation during metamorphism.

Identified August 11, 2026More metamorphic →

Explore Banded gneiss pebble 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

Formed when pre-existing igneous or sedimentary rock underwent intense heat and pressure, producing compositional layering and recrystallization. Individual gneiss bodies commonly formed during Precambrian to younger mountain-building events.

Uses & applications

Used as dimension stone, landscaping rock, paving, and aggregate; attractive polished pieces are collected as decorative specimens. This small rounded example has modest commercial value.

Geological facts

The irregular light-and-dark layers are gneissic banding, not sedimentary bedding. Its rounded shape indicates abrasion during transport in a river, beach, or glacial environment.

Field identification & locations

Identify it by coarse interlocking grains and alternating light quartz–feldspar bands with dark mica/amphibole bands; unlike slate, it does not split into thin sheets. Common in ancient continental shields and metamorphic mountain belts worldwide.