metamorphic

Small dark, banded rock (likely gneiss)

Probably biotite–quartz–feldspar gneiss; identification is uncertain from the small, blurred image.

AI-generated identification · may be incorrect

Dark gray to black with lighter streaks or bands and a dull, granular surface. Gneiss is typically Mohs 6–7, with interlocking quartz and feldspar grains and no prominent cleavage.

Identified September 28, 2026More metamorphic →

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Physical properties

Dark gray to black with lighter streaks or bands and a dull, granular surface. Gneiss is typically Mohs 6–7, with interlocking quartz and feldspar grains and no prominent cleavage.

Formation & geological history

Gneiss forms when existing rocks undergo intense heat and pressure, producing mineral banding; specimens can range widely in geological age.

Uses & applications

Gneiss is used as dimension stone, paving and aggregate; small pieces may be kept as geological samples.

Geological facts

The defining feature of gneiss is compositional banding, often alternating light quartz/feldspar and dark mica-rich layers.

Field identification & locations

Look for distinct light-and-dark mineral bands and a hard, crystalline texture; the image lacks enough detail for a confident identification. Gneiss occurs in ancient continental crust and mountain belts worldwide.