metamorphic
Slate
Foliated Metamorphic Rock (Mainly composed of Quartz, Illite, Chlorite)
Hardness: 2.5-4 Mohs; color: grey, black, or blue-grey; luster: dull to slightly pearly; crystal structure: microscopic crystals with strong slaty cleavage; cleavage: perfect basal cleavage allowing for thin sheets; specific gravity: 2.7–2.8
- Hardness
- 2
- Color
- grey, black, or blue-grey
- Luster
- dull to slightly pearly
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 2.5-4 Mohs; color: grey, black, or blue-grey; luster: dull to slightly pearly; crystal structure: microscopic crystals with strong slaty cleavage; cleavage: perfect basal cleavage allowing for thin sheets; specific gravity: 2.7–2.8
Formation & geological history
Formed through low-grade regional metamorphism of shale or mudstone under low pressure and temperature. Primarily found in tectonic regions like the Appalachian Mountains or Wales, UK.
Uses & applications
Used widely in roofing tiles, flooring, blackboards, billiard table tops, and garden landscaping due to its ability to split into thin slabs and its weather resistance.
Geological facts
Slate is the finest-grained foliated metamorphic rock. It retains the original bedding planes of the parent sedimentary rock but is reoriented by pressure to create a new planar surface of cleavage.
Field identification & locations
Identify in the field by its distinct ability to split along smooth, flat surfaces and its dull sound when struck (compared to the 'ring' of harder rocks). Common in mountain ranges and near ancient riverbeds. Collectors should look for fossils occasionally preserved in slate.
More like this
