metamorphic

Dark metamorphic rock, likely biotite-rich schist or amphibolite

Biotite–quartz–feldspar schist/amphibolite; exact identification requires testing

AI-generated identification · may be incorrect

Typically Mohs 5–6, dark gray to black, with a dull to slightly silky luster and foliated texture; visible platy mica or elongated amphibole grains may produce weak layering. The specimen appears fine- to medium-grained and weathered.

Identified August 31, 2026More metamorphic →

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At a glance

Common name: Dark metamorphic rock, likely biotite-rich schist or amphibolite
Scientific name: Biotite–quartz–feldspar schist/amphibolite; exact identification requires testing
Category: metamorphic
Identified: August 31, 2026
Method: Standard

AI Estimated Value

Approximately $1–$10 for a common hand specimen; $10–$40 if unusually attractive, labeled, or locality-documented.

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 shale or basaltic rock was subjected to elevated heat and pressure during regional metamorphism, commonly in Precambrian to Paleozoic mountain belts. Its precise age and protolith cannot be determined from the image.

Uses & applications

Used locally as crushed aggregate, fill, or decorative stone; attractive foliated pieces may be collected, though this example appears relatively ordinary and unsuitable for jewelry.

Geological facts

Biotite schist splits along mica-rich foliation, whereas amphibolite is generally tougher and dominated by hornblende and plagioclase. A streak, hardness, and mineral-grain examination would distinguish them.

Field identification & locations

Common in metamorphic terrains worldwide, including the Appalachian, Canadian Shield, Scandinavian, and Alpine regions. Check for foliation, mica flakes, amphibole prisms, and reaction to a steel knife; a fresh broken surface is most diagnostic.