metamorphic

Likely slate or fine-grained metamorphic rock

Slate; predominantly microcrystalline quartz, mica, and clay minerals

AI-generated identification · may be incorrect

Dark gray-green, dull to faintly silky luster, very fine grained, with planar foliation and irregular splitting; hardness about 3–6 depending on mica and quartz content. The pale vein is likely quartz or calcite.

Identified September 16, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or mudstone underwent low-grade regional metamorphism, typically during mountain building; its exact geological age cannot be determined from the image. Commonly develops strong slaty cleavage from aligned mica and clay minerals.

Uses & applications

Used for roofing, flooring, paving, writing boards, and architectural stone; attractive pieces may be collected, but this specimen appears to have little commercial value.

Geological facts

The layered appearance and thin, planar fracture are characteristic of slaty cleavage rather than sedimentary bedding. A white vein cutting across the rock formed later through fluid-filled fractures.

Field identification & locations

Common in metamorphic belts worldwide, including Wales, Vermont, Spain, Brazil, and India. Confirm with a streak/acid test: slate generally leaves a gray streak, while calcite veins fizz weakly in dilute hydrochloric acid; quartz does not.