metamorphic
Slate
Slate
Hardness: 2.5-4 Mohs; Color: Gray, bluish-gray, green, or purple; Luster: Dull; Structure: Foliated; Cleavage: Perfect slaty cleavage; Specific Gravity: 2.7-2.8
- Hardness
- 2
- Color
- Gray, bluish-gray, green, or purple
- Luster
- Dull
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Physical properties
Hardness: 2.5-4 Mohs; Color: Gray, bluish-gray, green, or purple; Luster: Dull; Structure: Foliated; Cleavage: Perfect slaty cleavage; Specific Gravity: 2.7-2.8
Formation & geological history
Formed through low-grade metamorphism of shale or mudstone under relatively low pressure and temperature conditions. It is typically associated with ancient mountain-building events (Orogenies).
Uses & applications
Extensively used for roofing shingles, floor tiles, blackboards, billiard table tops, and laboratory bench tops. Also used as decorative stone in landscaping.
Geological facts
Slate is unique because it can be split into very thin, flat sheets. Some of the highest quality slate in the world comes from Wales and Spain. It is nearly waterproof due to its high density.
Field identification & locations
Identify in the field by its characteristic ability to split into thin layers (platy fragments) and its dull, matte finish. Commonly found in mountainous regions or areas of former tectonic activity.
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