metamorphic

Likely gneiss (dark, fine-grained specimen)

Foliated metamorphic rock, probably biotite–quartz–feldspar gneiss; exact identification requires closer examination

AI-generated identification · may be incorrect

Dark gray to black with scattered pale mineral grains and a weak light-colored band; grains appear crystalline and the surface is dull to slightly sparkly. Hardness is likely about 6–7 Mohs if quartz- and feldspar-rich; crystal structure is granular, with no obvious cleavage in the whole rock.

Identified September 28, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when pre-existing rock was recrystallized under high heat and pressure deep in the crust; gneiss commonly records ancient metamorphic events, often billions to hundreds of millions of years old.

Uses & applications

Commonly used as dimension stone, paving, landscaping aggregate, and decorative stone; this small, unpolished specimen is mainly suitable for collecting.

Geological facts

The pale streak may reflect quartz or feldspar-rich layering, a typical feature of gneiss, though the image alone cannot confirm the rock type.

Field identification & locations

Look for alternating mineral-rich bands and interlocking grains; common in ancient continental shields and mountain belts. A fresh broken surface and magnification would help distinguish gneiss from other dark metamorphic rocks.