metamorphic
Slate
Slate (Metamorphic rock)
Hardness: 2.5-4 on Mohs scale. Color: Grey, dark blue-grey, greenish, or brownish. Luster: Dull to satiny. Texture: Very fine-grained, exhibiting planar foliation (slaty cleavage).
- Hardness
- 2
- Color
- Grey, dark blue-grey, greenish, or brownish
- Luster
- Dull to satiny
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Physical properties
Hardness: 2.5-4 on Mohs scale. Color: Grey, dark blue-grey, greenish, or brownish. Luster: Dull to satiny. Texture: Very fine-grained, exhibiting planar foliation (slaty cleavage).
Formation & geological history
Formed by low-grade regional metamorphism of shale or mudstone under relatively low temperature and pressure conditions, causing clay minerals to re-crystallize into fine micas.
Uses & applications
Widely used for roofing tiles, flooring, pool tables, laboratory table tops, blackboards, and decorative stone landscaping.
Geological facts
Slate can split into very thin, flat sheets due to its slaty cleavage. High quality natural slate is extremely durable and can last for well over a century when used as a roofing material.
Field identification & locations
Identified in the field by its fine grain, dull surface, and ability to break along flat, smooth parallel planes. Commonly found in mountainous or metamorphosed sedimentary terrains worldwide.
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