metamorphic

Weathered granitic gneiss

Quartz–feldspar–mica gneiss (compositionally granitic)

AI-generated identification · may be incorrect

Typically 6–7 Mohs; pale gray to cream with rusty iron-oxide staining, vitreous quartz and dull feldspar, plus darker mica/amphibole patches. Coarse crystalline texture and weakly visible foliation; no obvious cleavage as a whole rock.

Identified September 6, 2026More metamorphic →

Explore Weathered granitic 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 granite or related felsic igneous rock underwent high-grade metamorphism, recrystallizing quartz and feldspar and aligning mafic minerals. Such rocks commonly formed during Precambrian to Paleozoic mountain-building and were later exposed by uplift and erosion.

Uses & applications

Used locally as crushed aggregate, riprap, road stone, and occasionally dimension stone; attractive pieces may be collected, but it is not normally a jewelry material.

Geological facts

The orange-brown areas are likely limonite/goethite produced by weathering of iron-bearing minerals. The photograph alone cannot distinguish gneiss confidently from weathered granite or granitic migmatite.

Field identification & locations

Look for interlocking quartz and feldspar grains, dark mica/amphibole, and planar mineral alignment; a knife will not scratch quartz. Common in continental shields and metamorphic mountain belts; acid testing and a fresh broken surface improve identification.