metamorphic

Banded metamorphic rock, likely gneiss

Gneiss; predominantly quartz–feldspar with mica/amphibole minerals

AI-generated identification · may be incorrect

Hardness about 6–7 Mohs; gray to brown, coarse-grained, with alternating dark and light mineral bands and a dull to weakly vitreous luster. The specimen appears naturally weathered or tumbled, so cleavage and foliation are partly obscured.

Identified September 5, 2026More metamorphic →

Explore Banded metamorphic rock, likely 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 when pre-existing igneous or sedimentary rock underwent high-grade heat and pressure, causing mineral recrystallization and compositional banding. Gneiss commonly formed during Precambrian to younger mountain-building events.

Uses & applications

Used as building and paving stone, decorative aggregate, and landscaping material; attractive pieces are collected but generally have little gem value.

Geological facts

The diagnostic feature is gneissic banding: light quartz/feldspar layers alternating with darker biotite, amphibole, or pyroxene-rich layers. It can resemble banded granite, but the streaks are typically aligned and compositionally segregated.

Field identification & locations

Identify it by coarse interlocking grains and continuous or discontinuous light-dark bands; a glassy quartz streak and pale feldspar are common. Typical sources include ancient continental shields and metamorphic mountain belts worldwide.