sedimentary

Black Shale

Argillaceous Chert/Shale

Hardness: 3-5 Mohs, Color: Black to dark grey, Luster: Dull/Earthy, Structure: Fine-grained, fissile, Cleavage: Planar (slaty/fissile)

Identified July 9, 2026More sedimentary →

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Physical properties

Hardness: 3-5 Mohs, Color: Black to dark grey, Luster: Dull/Earthy, Structure: Fine-grained, fissile, Cleavage: Planar (slaty/fissile)

Formation & geological history

Formed from the compaction of silt and clay-size mineral particles. The black color indicates a high organic carbon content, typically deposited in deep-water, low-oxygen environments.

Uses & applications

Used as a source for natural gas and oil in the energy industry; can also be used in the manufacture of cement and bricks.

Geological facts

Black shale is often a primary source rock for petroleum and natural gas. Some varieties contain fossils such as graptolites or ancient plant remains.

Field identification & locations

Identify by its dark color, fine grain, and tendency to break into thin flat layers (fissility). It will not fizz with acid unless it contains calcite impurities.