metamorphic

Weathered iron-rich metamorphic rock (probable amphibolite or schist fragment)

Likely hornblende–plagioclase amphibolite with biotite/chlorite alteration; exact identification requires testing

AI-generated identification · may be incorrect

Dark brown-gray, fine- to medium-grained, dull to slightly silky luster, with weak foliation and rusty iron-oxide staining. Estimated hardness 5–6 Mohs; cleavage is not obvious and specific gravity is likely about 2.9–3.3.

Identified August 31, 2026More metamorphic →

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At a glance

Common name: Weathered iron-rich metamorphic rock (probable amphibolite or schist fragment)
Scientific name: Likely hornblende–plagioclase amphibolite with biotite/chlorite alteration; exact identification requires testing
Category: metamorphic
Identified: August 31, 2026
Method: Standard

AI Estimated Value

Usually $1–$10 as an unverified field specimen; perhaps $10–$30 if polished or demonstrably representative of a local geology.

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

Probably formed when basaltic or gabbroic rock was metamorphosed under moderate-to-high pressure and temperature, commonly during mountain building; its geological age cannot be determined from the photograph. Surface weathering produced the brown oxidation and rounded shape.

Uses & applications

Used locally as aggregate, riprap, or decorative stone; generally has little gemstone value unless unusually attractive or polished.

Geological facts

The specimen appears water-worn or strongly weathered, and the apparent banding may reflect metamorphic foliation rather than sedimentary layering.

Field identification & locations

Look for aligned dark amphibole or mica grains, a green-black interior on a fresh chip, and weak response to a steel scratch; it is not magnetic unless it contains appreciable magnetite. Common in metamorphic belts and stream gravels; a thin section or lab mineral analysis is needed for certainty.