metamorphic
Slate
Metamorphic Pelitic Rock
Hardness: 3-4 on the Mohs scale; Color: Grey, black, purple, green, or red; Luster: Dull to sub-mat; Crystal structure: Fine-grained, foliated (slaty cleavage); Specific gravity: 2.7-2.8
- Hardness
- 3-4 on the Mohs scale
- Color
- Grey, black, purple, green, or red
- Luster
- Dull to sub-mat
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Physical properties
Hardness: 3-4 on the Mohs scale; Color: Grey, black, purple, green, or red; Luster: Dull to sub-mat; Crystal structure: Fine-grained, foliated (slaty cleavage); Specific gravity: 2.7-2.8
Formation & geological history
Formed through low-grade regional metamorphism of pelitic rocks, such as shale or mudstone, subjected to moderate heat and directed pressure.
Uses & applications
Widely used for roofing, flooring, flagging, billiards tables, and blackboards.
Geological facts
Slate's property of slaty cleavage allows it to be split into thin, smooth sheets, making it historically and architecturally significant as a durable building material.
Field identification & locations
Easily identified by its distinct platy foliation and dull luster. Commonly found in mountainous regions and areas with a history of ancient sedimentary deposition and tectonic activity.
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