metamorphic
Slate
Metamorphic Pelitic Rock
Hardness of 3 to 4 on the Mohs scale, typically gray, black, green, or reddish in color, dull to sub-metallic luster, fine-grained foliated crystal structure, perfect parting along cleavage planes (slaty cleavage), specific gravity around 2.7 to 2.8.
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Physical properties
Hardness of 3 to 4 on the Mohs scale, typically gray, black, green, or reddish in color, dull to sub-metallic luster, fine-grained foliated crystal structure, perfect parting along cleavage planes (slaty cleavage), specific gravity around 2.7 to 2.8.
Formation & geological history
Formed through the regional metamorphism of low-grade argillaceous rocks, principally shale or mudstone, subjected to moderate heat and differential pressure. Formed over hundreds of millions of years in ancient sedimentary basins.
Uses & applications
Widely used in construction for roofing, flooring, and paving, as well as in electrical panels, billiard tables, and blackboards.
Geological facts
Slate's ability to be split into thin, durable sheets has made it a primary building material for centuries, particularly in European architecture.
Field identification & locations
Easily identified by its fine-grained texture, ability to split into flat sheets (slaty cleavage), and dull ring when struck. Found globally in regions with ancient mountain-building events.
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