metamorphic

Banded gneiss

Gneiss, commonly quartz–feldspar–biotite gneiss

AI-generated identification · may be incorrect

Typically medium- to coarse-grained with alternating light quartz/feldspar and dark biotite or amphibole bands; vitreous to pearly luster, blocky fracture, and Mohs hardness about 6–7. The specimen’s strong foliation and compositional banding are characteristic, though exact minerals require testing.

Identified August 16, 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

Formed by high-grade regional metamorphism that recrystallized and segregated a preexisting igneous or sedimentary rock under intense heat and pressure. Gneiss commonly records Precambrian to younger continental mountain-building events.

Uses & applications

Used as dimension stone, facing stone, paving, landscaping rock, and aggregate; attractive polished pieces are collected but are generally not used as gemstones.

Geological facts

Its banding is metamorphic, not ordinary sedimentary layering: minerals were stretched, recrystallized, and aligned during deformation. It can grade into migmatite where partial melting occurred.

Field identification & locations

Identify it by distinct light–dark mineral bands, coarse crystals, and foliation; unlike granite, the bands are usually visibly deformed or streaked. Common in ancient continental shields and metamorphic mountain belts worldwide.