sedimentary

Sedimentary Strata of the Badlands (Mudstone, Siltstone, and Sandstone)

White River Group (Brule and Chadron Formations)

AI-generated identification · may be incorrect

Hardness: 2-3 (soft/crumbly); Color: Tan, gray, white, and reddish-pink bands; Luster: Dull/Earthy; Crystal Structure: Amorphous/Granular; Cleavage: None (friable).

Hardness: 2-3 (soft/crumbly)
Color: Tan, gray, white, and reddish-pink bands
Luster: Dull/Earthy

Identified June 8, 2026More sedimentary →

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Physical properties

Hardness: 2-3 (soft/crumbly); Color: Tan, gray, white, and reddish-pink bands; Luster: Dull/Earthy; Crystal Structure: Amorphous/Granular; Cleavage: None (friable).

Formation & geological history

Formed during the Late Eocene and Oligocene epochs (approx. 30-37 million years ago). Deposition occurred via ancient river floodplains and volcanic ash falls, followed by rapid erosion by wind and water.

Uses & applications

Primarily significant for scientific research, paleontology, and tourism. Not used in construction due to high clay content and low structural integrity.

Geological facts

This landscape is one of the world's richest fossil beds, containing remains of ancient horses, rhinos, and saber-toothed cats. The 'Red Layer' represents ancient fossilized soils (paleosols).

Field identification & locations

Identify by distinct horizontal multi-colored banding and steep, eroded 'spires' or 'buttes'. Found famously in South Dakota, USA. Collectors should note that it is illegal to remove specimens from National Parks.