metamorphic

Banded metamorphic rock, likely gneiss or banded amphibolite

Quartz–feldspar–biotite gneiss or amphibolite; exact identification requires thin-section or mineral tests

AI-generated identification · may be incorrect

Dark gray to black, fine- to medium-grained, with contrasting pale quartz/feldspar-rich bands or veins. Likely Mohs hardness 5–7, subvitreous to dull luster, weak-to-moderate foliation, and no obvious cleavage in the whole specimen.

Identified September 5, 2026More metamorphic →

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At a glance

Common name: Banded metamorphic rock, likely gneiss or banded amphibolite
Scientific name: Quartz–feldspar–biotite gneiss or amphibolite; exact identification requires thin-section or mineral tests
Category: metamorphic
Identified: September 5, 2026
Method: Standard

AI Estimated Value

About $2–$15 as a common hand specimen; $20–$75 if polished, unusually patterned, or confirmed as a distinctive locality specimen.

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 pre-existing igneous or sedimentary rock underwent high-grade regional metamorphism, producing mineral segregation and deformation; age cannot be determined from the photograph and may range from Precambrian to younger.

Uses & applications

Used locally as dimension stone, aggregate, landscaping stone, and geological teaching material; attractive banded pieces may be polished, but this example appears to have modest commercial value.

Geological facts

The pale bands may be quartz–feldspar leucosomes or quartz veins, while the dark matrix may contain biotite, hornblende, and plagioclase. A magnet could reveal abundant magnetite or iron-rich amphibole.

Field identification & locations

Common in Precambrian shields and deeply eroded mountain belts worldwide. Identify by strong compositional banding/foliation, glassy quartz grains, and testing hardness; acid reaction is generally absent.