sedimentary

Shale fragment

Shale (Laminated Mudstone)

Hardness: 3 on Mohs scale; Color: Grey to brownish-grey; Luster: Dull/Earthy; Structure: Clastic, laminated; Cleavage: Fissile, splits easily into thin plates.

Hardness: 3 on Mohs scale
Color: Grey to brownish-grey
Luster: Dull/Earthy

Identified July 20, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Grey to brownish-grey; Luster: Dull/Earthy; Structure: Clastic, laminated; Cleavage: Fissile, splits easily into thin plates.

Formation & geological history

Formed from the compaction of silt and clay-size mineral particles (mud) in slow-moving water environments such as lake bottoms or river deltas. Often dates from various eras, commonly Palaeozoic or Mesozoic.

Uses & applications

Used in the production of cement, bricks, and tiles. Some organic-rich shales are sources of oil and natural gas (shale gas).

Geological facts

Shale is the most common sedimentary rock on Earth, comprising about 70 percent of the rocks in the Earth's crust. It often contains well-preserved fossils.

Field identification & locations

Identify in the field by its thin layers (fissility) and soft, earthy texture. Common in sedimentary basins worldwide. Often breaks into flat, thin flakes.