sedimentary

Shale

Sedimentary pelitic rock

Hardness: 3 on Mohs scale. Color: Gray, brown, black, green, or red. Luster: Dull or earthy. Structure: Fissile, platy, or thinly laminated. Cleavage: Well-developed parallel to bedding planes. Specific gravity: 2.0 to 2.8.

Hardness: 3 on Mohs scale
Color: Gray, brown, black, green, or red
Luster: Dull or earthy

Identified August 3, 2026More sedimentary →

Explore Shale in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed from the compaction of silt and clay-size mineral particles (mud) over millions of years in quiet depositional environments such as lakes, river deltas, lagoons, and deep ocean basins.

Uses & applications

Used in the manufacturing of bricks, tiles, and pottery; as a source of filler in cement; and increasingly as a source of oil and natural gas through fracking.

Geological facts

Shale is the most abundant sedimentary rock on Earth, making up over 70 percent of sedimentary rock crust. It often contains well-preserved fossils due to the fine-grained nature of its original sediments.

Field identification & locations

Easily identified by its fine layers and tendency to split into thin, flat pieces (fissility). Common worldwide, especially in areas with ancient lake or marine beds.