metamorphic
Slate
Slate
Hardness: 2.5-4 (Mohs scale), Color: Dark grey to black, Luster: Dull to pearly on cleavage surfaces, Structure: Fine-grained with slaty cleavage, Specific Gravity: 2.7-2.8
- Hardness
- 2
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Physical properties
Hardness: 2.5-4 (Mohs scale), Color: Dark grey to black, Luster: Dull to pearly on cleavage surfaces, Structure: Fine-grained with slaty cleavage, Specific Gravity: 2.7-2.8
Formation & geological history
Formed through low-grade regional metamorphism of shale or mudstone under relatively low temperature and pressure conditions. Often found in folded mountain belts.
Uses & applications
Used for roofing tiles, flooring, electrical panels, billiard table tops, and blackboards due to its ability to be split into thin, flat sheets.
Geological facts
Slate was used as the primary writing surface in schools (the 'slate board') before the invention of paper notebooks became affordable.
Field identification & locations
Identify by its ability to split into thin sheets (slaty cleavage) and the 'ping' sound it makes when struck. Common in the Appalachian Mountains, Wales, and Brazil.
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