metamorphic
Slate
Slate
Hardness: 2.5-4; Color: Grey, black, or blue-grey; Luster: Dull to satiny; Structure: Foliated with distinct slaty cleavage; SG: 2.7-2.8
- Hardness
- 2
- Color
- Grey, black, or blue-grey
- Luster
- Dull to satiny
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Physical properties
Hardness: 2.5-4; Color: Grey, black, or blue-grey; Luster: Dull to satiny; Structure: Foliated with distinct slaty cleavage; SG: 2.7-2.8
Formation & geological history
Formed through the low-grade metamorphism of shale or mudstone under regional heat and pressure, often during mountain-building events.
Uses & applications
Widely used in construction for roofing shingles, flooring, hearths, and historically as chalkboards and laboratory bench tops.
Geological facts
Slate naturally splits into thin, flat sheets due to its slaty cleavage, making it an ideal material for traditional roofing that can last over a century.
Field identification & locations
Identify by its ability to split into thin sheets and its dull sound when struck. Common in metamorphic belts such as the Appalachians or Wales.
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