sedimentary

Claystone River Rock

Claystone (Indurated Mud)

Hardness: 2.5–3 on Mohs scale; Color: Reddish-brown to dark brown; Luster: Dull/Earthy; Structure: Massive, fine-grained; Specific Gravity: Approx 2.3–2.6

Hardness: 2
Color: Reddish-brown to dark brown
Luster: Dull/Earthy

Identified July 6, 2026More sedimentary →

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Physical properties

Hardness: 2.5–3 on Mohs scale; Color: Reddish-brown to dark brown; Luster: Dull/Earthy; Structure: Massive, fine-grained; Specific Gravity: Approx 2.3–2.6

Formation & geological history

Formed through the lithification of mud and silt deposits, typically in low-energy environments like lake beds or floodplains. This specimen has been rounded through water erosion in a river or stream channel.

Uses & applications

Large-scale use involves the manufacturing of bricks, terracotta, and cement; small smooth specimens are used in landscaping or as decorative pocket stones.

Geological facts

Claystone differs from shale because it lacks the 'fissility' or the ability to split into thin layers. It is essentially compressed mud that has turned to stone over millions of years.

Field identification & locations

Identify by its smooth, matte texture and lack of visible grains. It can often be scratched with a copper penny or steel knife. Common in riverbeds globally where sedimentary outcrops exist.