sedimentary

Ironstone Concretion (Coprolite-like)

Goethite/Hematite Siderite Spheroid (FeCO3 or FeO(OH))

AI-generated identification · may be incorrect

Hardness: 4-5.5 (Mohs scale), Color: Rusty brown to dark chocolate, Luster: Dull/Sub-metallic, Structure: Botryoidal or concretionary, Specific Gravity: 3.0-4.3

Hardness: 4-5

Identified June 4, 2026More sedimentary →

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Physical properties

Hardness: 4-5.5 (Mohs scale), Color: Rusty brown to dark chocolate, Luster: Dull/Sub-metallic, Structure: Botryoidal or concretionary, Specific Gravity: 3.0-4.3

Formation & geological history

Formed by the precipitation of mineral cement within the spaces between particles in sedimentary beds, often around a nucleus. These specifically resemble 'coprolites' but are usually inorganic geological formations.

Uses & applications

Primarily used as geological curiosities for collectors; historically some iron-rich nodules were used as low-grade iron ore.

Geological facts

Many of these nodules are mistakenly identified as fossilized dung (coprolites) due to their rounded, lumpy shapes and brown color. They represent localized concentrations of iron-bearing minerals that are harder than the surrounding host rock.

Field identification & locations

Identify by its unusually high weight (density) compared to common pebbles and its distinctive lumpy 'brain-like' or botryoidal surface. Often found in shale or sandstone units.