metamorphic

Dark gray foliated metamorphic rock, likely slate or phyllite

Slate/phyllite; commonly quartz, muscovite/illite, chlorite, and graphite or carbonaceous matter

AI-generated identification · may be incorrect

Fine-grained, dark gray, silky to dull luster with visible planar foliation; slate has hardness ~3–4 and excellent cleavage, while phyllite is slightly softer and more lustrous. The blurred image prevents confident separation from schist.

Identified August 11, 2026More metamorphic →

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At a glance

Common name: Dark gray foliated metamorphic rock, likely slate or phyllite
Scientific name: Slate/phyllite; commonly quartz, muscovite/illite, chlorite, and graphite or carbonaceous matter
Category: metamorphic
Identified: August 11, 2026
Method: Standard

AI Estimated Value

$5–$30 for common hand specimens; $30–$100+ for polished, unusually colored, or well-displayed pieces.

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

Forms when shale or mudstone is regionally metamorphosed under low-grade pressure and heat, typically during mountain building; age depends on the source terrain and may range from Paleozoic to Precambrian.

Uses & applications

Used for roofing, floor and wall tiles, paving, blackboards, landscaping, and architectural cladding; attractive phyllite may be collected as a specimen.

Geological facts

Foliation records directed tectonic pressure, and slate commonly splits into thin, flat sheets. Phyllite represents a higher metamorphic grade than slate.

Field identification & locations

Look for strong, closely spaced planar splitting and a fine texture; a silky sheen suggests phyllite, whereas very smooth dull cleavage suggests slate. Common worldwide in metamorphic belts, including Wales, Vermont, Spain, and Brazil.