metamorphic

Polished banded gneiss or amphibolite specimen

Biotite–quartz–feldspar gneiss, possibly amphibole-rich; exact identification requires testing

AI-generated identification · may be incorrect

Dark gray to brown, elongated and highly rounded/polished, with pale streaky mineral bands and a dull to slightly silky luster. Likely Mohs hardness 5.5–7; minerals show flattened, aligned grains rather than distinct crystals, with no obvious cleavage on the surface.

Identified September 4, 2026More metamorphic →

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At a glance

Common name: Polished banded gneiss or amphibolite specimen
Scientific name: Biotite–quartz–feldspar gneiss, possibly amphibole-rich; exact identification requires testing
Category: metamorphic
Identified: September 4, 2026
Method: Standard

AI Estimated Value

Approximately $10–$40 as a polished decorative specimen; larger, unusually patterned pieces may reach $50–$100.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Formed when preexisting igneous or sedimentary rock underwent intense regional metamorphism, producing foliation and mineral segregation during mountain building, typically hundreds of millions to billions of years ago. Its shape is human-worked or water-rounded rather than natural outcrop form.

Uses & applications

Used as a decorative stone, paperweight, massage stone, or lapidary specimen; comparable rock is also used for aggregate, dimension stone, and landscaping. Value is generally modest unless unusually attractive or historically documented.

Geological facts

The light-dark banding reflects metamorphic foliation, commonly involving quartz, feldspar, mica, and/or amphibole. A streaky texture distinguishes gneiss from homogeneous basalt or ordinary granite.

Field identification & locations

Look for interlocking grains and compositional banding; a steel nail generally will not scratch it, while quartz-rich areas can scratch glass. Common worldwide in ancient continental shields and metamorphic mountain belts.