metamorphic

Banded metamorphic rock, likely gneiss or migmatitic gneiss

Quartz–feldspar–mica gneiss; exact identification requires a fresh surface and mineral tests

AI-generated identification · may be incorrect

The specimen shows coarse, interlocking light tan and dark gray bands with a granular, dull-to-subvitreous luster, consistent with quartz, feldspar, and biotite/amphibole. Hardness is approximately 6–7 Mohs; cleavage is weak overall, though feldspar and mica may cleave.

Identified September 8, 2026More metamorphic →

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At a glance

Common name: Banded metamorphic rock, likely gneiss or migmatitic gneiss
Scientific name: Quartz–feldspar–mica gneiss; exact identification requires a fresh surface and mineral tests
Category: metamorphic
Identified: September 8, 2026
Method: Standard

AI Estimated Value

About $1–$10 for a common hand specimen; $10–$50 for attractive polished or strongly banded examples.

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 high-grade heat and pressure, producing mineral segregation and foliation, commonly during Precambrian to Paleozoic mountain-building events.

Uses & applications

Used as crushed aggregate, dimension stone, paving, landscaping rock, and occasionally decorative facing stone; attractive pieces are collected but are not usually gemstones.

Geological facts

Gneiss commonly preserves alternating felsic and mafic layers created by metamorphic recrystallization. The rounded edges indicate natural weathering or tumbling rather than a sharply broken hand specimen.

Field identification & locations

Look for planar or wavy light–dark banding, visible quartz/feldspar grains, and mica flakes; it is common in ancient continental shields and metamorphic mountain belts worldwide. A polished or fresh face and a hardness test help distinguish it from banded sedimentary rock.