metamorphic

Dark metamorphic rock, likely biotite schist or hornblende-bearing gneiss

Probable mica schist/amphibolite; composition may include biotite, amphibole, quartz, feldspar, and iron oxides

AI-generated identification · may be incorrect

Dark gray-black, fine- to medium-grained, with weak foliation and small reflective or rusty brown mineral patches; likely Mohs 5–6, vitreous to submetallic luster, and no obvious cleavage visible at this scale.

Identified September 5, 2026More metamorphic →

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At a glance

Common name: Dark metamorphic rock, likely biotite schist or hornblende-bearing gneiss
Scientific name: Probable mica schist/amphibolite; composition may include biotite, amphibole, quartz, feldspar, and iron oxides
Category: metamorphic
Identified: September 5, 2026
Method: Standard

AI Estimated Value

About $1–$10 as a common hand specimen; potentially $10–$30 if unusually attractive, locality-labeled, or confirmed mineralogically.

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/protolithic rocks were subjected to elevated pressure and temperature during regional metamorphism, commonly from Precambrian to Paleozoic mountain-building events.

Uses & applications

Usually used as a decorative or educational specimen; larger, sound blocks of related gneiss or amphibolite may serve as crushed stone, aggregate, or dimension stone.

Geological facts

The dark minerals are probably biotite mica or hornblende, while rusty areas likely represent weathered iron-bearing minerals. Exact identification requires a fresh surface, hand lens, streak, hardness, and ideally thin-section or chemical testing.

Field identification & locations

Look for planar foliation, sparkly mica flakes, amphibole crystals, and a lack of vesicles or sedimentary layering; common in metamorphic belts worldwide. It is unlikely to have significant gem value.