metamorphic
Slate
Metamorphic mudstone or shale
Hardness: 3-4 on Mohs scale. Color: typically gray, greenish-gray, black, purple, or red. Luster: dull to fine satin. Crystal structure: fine-grained, foliated. Cleavage: excellent slaty cleavage.
- Hardness
- 3-4 on Mohs scale
- Color
- typically gray, greenish-gray, black, purple, or red
- Luster
- dull to fine satin
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Physical properties
Hardness: 3-4 on Mohs scale. Color: typically gray, greenish-gray, black, purple, or red. Luster: dull to fine satin. Crystal structure: fine-grained, foliated. Cleavage: excellent slaty cleavage.
Formation & geological history
Formed by regional metamorphism of low-grade mudstone or shale, typically subjected to moderate heat and directed pressure over millions of years during mountain building events.
Uses & applications
Used historically and modernly for roofing, flooring, paving, pool tables, blackboards, and decorative stone.
Geological facts
Slate's ability to split into thin, flat sheets makes it exceptionally useful in construction and architectural applications for centuries.
Field identification & locations
Identify in the field by its distinct planar foliation (slaty cleavage), fine-grained texture, and dull ringing sound when struck.
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