metamorphic

Polished banded gneiss or schist pebble

Banded quartz–feldspar–mica gneiss (tentative)

AI-generated identification · may be incorrect

Typically Mohs 6–7; gray, tan, black, and rusty-brown bands with a dull to silky luster and strong foliation. Quartz and feldspar provide hardness, while mica produces the layered texture; apparent holes may be weathering pits or mica partings.

Identified September 12, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when preexisting igneous or sedimentary rock underwent intense heat and pressure, recrystallizing and segregating minerals into bands; age cannot be determined from the photograph. The specimen appears naturally water-worn and possibly lightly polished.

Uses & applications

Used as decorative stone, landscaping aggregate, cabochons, and collectible specimens; large sound blocks may be used for building stone. This small piece has modest commercial value.

Geological facts

The alternating light and dark layers are diagnostic of metamorphic compositional banding, rather than sedimentary bedding. Rust colors commonly result from oxidation of iron-bearing minerals.

Field identification & locations

Look for interlocking grains, aligned mica flakes, and irregular light–dark banding; unlike slate, it is coarser and unlike granite, it is distinctly foliated. Common in Precambrian metamorphic terrains and glacial or river gravels worldwide.