sedimentary

Shale or Siltstone

Fine-grained siliciclastic sedimentary rock

Hardness: 3 on Mohs scale; Color: Light gray-green with a brown weathered portion; Luster: Dull or earthy; Crystal structure: Microcrystalline to cryptocrystalline clay minerals; Cleavage: Fissile or parallel bedding planes.

Hardness: 3 on Mohs scale
Color: Light gray-green with a brown weathered portion
Luster: Dull or earthy

Identified August 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the compaction of silt and clay-sized mineral particles (mud) that settled in quiet depositional environments such as lakes, lagoons, or deep marine basins, typically over millions of years.

Uses & applications

Used primarily in the manufacture of ceramics, bricks, cement, and as a source rock for hydrocarbons (oil and natural gas).

Geological facts

Shale is the most abundant sedimentary rock on Earth, making up over 70 percent of the Earth's crustal sedimentary rocks. It often preserves exceptionally detailed fossils due to the fine grain size of the sediment.

Field identification & locations

Can be identified in the field by its fine-grained texture, layered appearance, and tendency to break into thin, parallel plates or flakes. Common worldwide in sedimentary basins.

Other sedimentary specimens

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Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

fossil

Quartz pebble

Silicon dioxide (SiO2)

sedimentary

Sedimentary Sandstone

Arenite (Sedimentary Rock)

sedimentary

Generic Pebble / Rock Fragment

Lithic fragment / Weathered rock

sedimentary

Banded Siltstone / Mudstone Pebble

Siltstone / Argillite

sedimentary