metamorphic

Slate

Foliated Metamorphic Rock (composed of quartz, illite, chlorite)

AI-generated identification · may be incorrect

Hardness: 2.5-4 Mohs; Color: Dark grey to black; Luster: Dull to satiny; Structure: Foliated with fine grains; Cleavage: Perfect slaty cleavage (breaks into flat planes)

Hardness: 2
Color: Dark grey to black
Luster: Dull to satiny

Identified July 18, 2026More metamorphic →

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Physical properties

Hardness: 2.5-4 Mohs; Color: Dark grey to black; Luster: Dull to satiny; Structure: Foliated with fine grains; Cleavage: Perfect slaty cleavage (breaks into flat planes)

Formation & geological history

Formed by low-grade regional metamorphism of shale or mudstone under low pressure and temperature conditions, typically in sedimentary basins.

Uses & applications

Extensively used for roofing tiles, flooring, electrical panels, chalkboards, and decorative landscaping.

Geological facts

Slate is renowned for its ability to split into thin, durable sheets. It was the primary material for school writing tablets throughout the 19th century.

Field identification & locations

Check for fine-grained texture and the ability to split into thin sheets along parallel planes. Found in metamorphic belts like the Appalachians or Wales.