metamorphic

Dark slate (probable)

Slate, a fine-grained metamorphic rock composed mainly of mica-group minerals and quartz; exact identification is uncertain from the photograph.

AI-generated identification · may be incorrect

Dark gray to charcoal, dull to slightly silky, very fine-grained, with prominent planar splitting/foliation and pale vein-like markings. Slate is typically Mohs 3–4, with microscopic aligned mica crystals; specific gravity is about 2.7–2.8.

Identified October 5, 2026More metamorphic →

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At a glance

Common name: Dark slate (probable)
Scientific name: Slate, a fine-grained metamorphic rock composed mainly of mica-group minerals and quartz; exact identification is uncertain from the photograph.
Category: metamorphic
Identified: October 5, 2026
Method: Standard

AI Estimated Value

About $1–$10 for a common unlabelled hand specimen; more if its locality or geological context is 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

Forms when shale or mudstone is compressed and mildly metamorphosed, producing slaty cleavage. Its age depends on the source formation and cannot be determined from the image.

Uses & applications

Used for roofing, floor and paving tiles, blackboards, and decorative stone; this rough fragment is mainly suitable for study or collecting.

Geological facts

The flat cleavage surfaces reflect microscopic platy minerals aligned during low-grade metamorphism; the pale streaks may be quartz or calcite veins.

Field identification & locations

The long, planar surfaces and fine texture support slate, though the angular fractures and veins could also indicate another foliated rock. Check whether it splits into thin, flat sheets and whether a fresh surface is fine-grained; common sources include slate belts worldwide. The French note requests a better macroscopic description but gives no locality or physical tests.