metamorphic
Slate
Metamorphic Mudstone / Shale
Hardness: 2.5-4 on Mohs scale. Color: Blue-gray to dark purple-gray. Luster: Dull, earthy. Structure: Foliated, fine-grained. Cleavage: Perfect slaty cleavage, splits into flat sheets.
- Hardness
- 2
- Color
- Blue-gray to dark purple-gray
- Luster
- Dull, earthy
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Physical properties
Hardness: 2.5-4 on Mohs scale. Color: Blue-gray to dark purple-gray. Luster: Dull, earthy. Structure: Foliated, fine-grained. Cleavage: Perfect slaty cleavage, splits into flat sheets.
Formation & geological history
Formed through low-grade regional metamorphism of shale, mudstone, or siltstone under low heat and pressure conditions. Commonly found in ancient sedimentary basins that experienced tectonic compression.
Uses & applications
Widely used for roofing tiles, flooring, flagstones, outdoor landscaping, billiards tables, blackboards, and decorative stone items.
Geological facts
Slate can split into very thin, flat sheets due to its slaty cleavage, making it a classic architectural material for centuries. Its color varies depending on mineral impurities like iron oxides or organic carbon.
Field identification & locations
Identified by its fine-grained texture, dull surface, flat rounded pebble form, and distinct blue-gray to purplish tone. Commonly found on riverbeds, beaches, and in slate quarry regions worldwide.
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