sedimentary

Sandstone Pebble with Iron Staining

Clastic Sedimentary Rock (primarily Quartz with Fe2O3 oxides)

Hardness: 6-7 (Mohs scale); Color: Tan to grey with reddish-brown concentric or spiral swirl patterns; Luster: Dull/Earthy; Structure: Granular/Clastic texture; Cleavage: None; Specific Gravity: 2.2-2.8

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

Identified March 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and cementation of mineral particles (sand), likely in a marine or riverine environment. The distinctive swirling patterns are Liesegang rings, formed by the rhythmic precipitation of iron oxides (hematite or limonite) from groundwater moving through the porous rock.

Uses & applications

Used primarily as decorative landscaping stones, aquarium decor, or as pocket stones/curiosities for beachcombers.

Geological facts

The spiral 'S' pattern visible on this specimen is a classic example of chemical weathering and fluid flow. While they often look like fossils (specifically snail shells), they are actually geochemical 'pseudo-fossils' created by mineral-rich water.

Field identification & locations

Identify in the field by the grainy sandpaper-like texture and the presence of localized iron-oxide banding. Commonly found on beaches, riverbeds, and in arid basins where selective mineralization occurs.

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