metamorphic

Likely weathered gneiss

Banded quartz–feldspar–mica gneiss

AI-generated identification · may be incorrect

Hardness about 6–7 Mohs; gray, white, and rusty-brown surface with weak foliation and coarse interlocking grains. Quartz and feldspar are glassy to dull; mica may produce subtle sparkles, while brown staining is likely iron oxide.

Identified September 21, 2026More metamorphic →

Explore Likely weathered 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 preexisting igneous or sedimentary rock underwent intense regional metamorphism at high temperature and pressure, commonly during Precambrian to Paleozoic mountain-building. Surface oxidation and weathering produced the rusty patches.

Uses & applications

Used locally as crushed stone, road aggregate, riprap, building stone, and landscaping rock; attractive pieces may be polished as decorative stone. This hand specimen has little commercial value unless unusually patterned or from a notable locality.

Geological facts

Gneiss commonly preserves alternating mineral-rich bands or stretched lenses, though weathering can obscure them. It is distinguished from granite by foliation and from schist by its generally coarser grains and less pronounced platy texture.

Field identification & locations

Look for compositional banding, abundant quartz and feldspar, mica flakes, and a hard, irregular fracture; a streak, acid test, and fresh broken surface would improve identification. Common worldwide in ancient continental shields and metamorphic mountain belts.