sedimentary

Ferruginous Sandstone (Ironstone Nodules)

Ferruginous Quartz-Arenite (with Goethite/Hematite cement)

AI-generated identification · may be incorrect

Hardness: 5-6 (variable based on cement); Color: Dark brown to black weathering rinds with orange/tan interior; Luster: Dull to sub-earthy; Structure: Clastic, often rounded by water/erosion; Cleavage: None (concretionary fracture).

Hardness: 5-6 (variable based on cement)
Luster: Dull to sub-earthy

Identified March 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when iron-rich groundwater precipitates iron oxides (like limonite or goethite) within the pore spaces of sandstone layers. These often form as concretions that are harder than the surrounding rock, lasting millions of years after the host rock has eroded.

Uses & applications

Primarily used as a minor iron ore historically; currently used in decorative landscaping, as construction fill, or as geological curiosities for collectors.

Geological facts

These are often mistaken for meteorites due to their dark, pitted 'fusion crust' appearance, but they are entirely terrestrial. They are sometimes called 'shaman stones' or 'Moqui marbles' in specific regions like Utah.

Field identification & locations

Identify in the field by checking for a 'rusty' streak (brownish-orange) when rubbed against unglazed porcelain and observing the sandy texture inside. Commonly found in riverbeds and desert pavement areas where softer rock has weathered away.