sedimentary
Sedimentary Strata of the Badlands (Mudstone, Siltstone, and Sandstone)
White River Group (Brule and Chadron Formations)
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
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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.
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