metamorphic

Banded metamorphic rock, likely gneiss

Foliated gneiss; chiefly quartz, feldspar, and dark mica/amphibole

AI-generated identification · may be incorrect

Hardness about 6–7 Mohs; coarse-grained, gray-green and cream bands, with a dull to slightly glassy luster. The alternating mineral layers indicate foliation; cleavage is mainly within mica-rich zones, and specific gravity is approximately 2.6–2.8.

Identified September 2, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when preexisting igneous or sedimentary rock underwent intense heat and pressure, producing mineral segregation and banding. Its exact geological age cannot be determined from the photograph; gneisses range from Archean to recent metamorphic events.

Uses & applications

Used as crushed aggregate, dimension stone, landscaping rock, and occasionally as decorative polished material; this small, weathered specimen has mainly educational or collector value.

Geological facts

The light bands are commonly quartz and feldspar, while darker bands contain biotite, amphibole, or other ferromagnesian minerals. Strong compositional banding distinguishes gneiss from more weakly foliated schist.

Field identification & locations

Identify it by visible alternating light and dark mineral bands, coarse interlocking grains, and resistance to scratching by ordinary steel. Common in ancient continental shields and high-grade mountain belts worldwide.