metamorphic

Slate

Slate; predominantly fine-grained phyllosilicates, commonly muscovite/illite and chlorite with quartz

AI-generated identification · may be incorrect

Very fine-grained, gray-brown, dull to silky luster, low-grade metamorphic foliation and strong slaty cleavage visible as thin layers. Hardness is about 3–4 Mohs; specific gravity approximately 2.7–2.8.

Identified September 19, 2026More metamorphic →

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At a glance

Common name: Slate
Scientific name: Slate; predominantly fine-grained phyllosilicates, commonly muscovite/illite and chlorite with quartz
Category: metamorphic
Identified: September 19, 2026
Method: Standard

AI Estimated Value

About $1–$10 for a common loose specimen; $10–$50 for attractive hand samples or unusual colors, while architectural-grade slabs are priced separately.

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 mudstone undergoes low-grade regional metamorphism, typically during mountain building. Its exact geological age cannot be determined from the photograph; slate occurs in rocks ranging from Precambrian to recent mountain belts.

Uses & applications

Used for roofing, flooring, paving, wall cladding, gravestones, pool tables, and decorative tiles; attractive pieces are collected but usually have modest value.

Geological facts

The specimen’s planar splitting and fine layering are characteristic of slaty cleavage, produced by aligned microscopic clay-derived minerals rather than original sedimentary bedding.

Field identification & locations

Identify it by its fine texture, layered appearance, and ability to split into thin, relatively flat sheets; it commonly occurs in metamorphic belts worldwide, including Wales, Vermont, Spain, Brazil, and China.