Sedimentary

Siltstone/Sandstone (possibly Wonderstone or Picture Sandstone)

Clastic Sedimentary Rock (primarily SiO2 with Iron Oxide inclusions)

Hardness: 6-7 (Mohs scale); Color: Light grey to tan with concentric brown/purple curved bands (Liesegang rings); Luster: Dull/Earthy; Structure: Fine-grained clastic; Cleavage: None, exhibits conchoidal or irregular fracture.

Hardness: 6-7 (Mohs scale)
Luster: Dull/Earthy

Identified March 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and cementation of fine-grained mineral particles (silt/sand). The unique banding is caused by rhythmic precipitation of iron or manganese oxides within the porous rock via groundwater, known as Liesegang rings. Common in Paleozoic to Mesozoic formations.

Uses & applications

Used primarily for decorative purposes, garden landscaping, or as lapidary material for cabochons and 'picture' stones. Larger deposits are used as building stone or crushed for construction aggregate.

Geological facts

The curved bands are chemical artifacts and do not represent the original bedding planes of the sediment. These patterns are often mistaken for fossils or wood grain.

Field identification & locations

Identify in the field by its gritty texture and the presence of colorful, concentric, or wavy bands. Commonly found in arid environments such as Utah and Nevada (USA) or South Africa. Collectors should look for high-contrast banding and lack of cracks.

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