sedimentary

Ironstone Nodules (Limonite/Hematite)

Goethite/Hematite mix (FeO(OH)/Fe2O3)

AI-generated identification · may be incorrect

Hardness: 5-5.5 on Mohs scale; Color: Dark brown to reddish-orange; Luster: Dull, earthy, or sub-metallic; Structure: Often concretionary or massive; Specific Gravity: 3.3-4.3.

Hardness: 5-5
Color: Dark brown to reddish-orange
Luster: Dull, earthy, or sub-metallic

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 5-5.5 on Mohs scale; Color: Dark brown to reddish-orange; Luster: Dull, earthy, or sub-metallic; Structure: Often concretionary or massive; Specific Gravity: 3.3-4.3.

Formation & geological history

Formed by the precipitation of iron oxide minerals from groundwater within sedimentary rock layers, often around a nucleus like a leaf, shell, or pebble. Often dating from the Cretaceous to the Quaternary periods.

Uses & applications

Historically used as a low-grade iron ore; commonly used today in landscaping, as a decorative mineral for hobbyists, or as 'paint stones' due to their pigment quality.

Geological facts

These nodules are often mistaken for meteorites due to their heavy weight and dark, weathered 'fusion crust' look. Also known as 'Moqui marbles' in specific regions like Utah.

Field identification & locations

Identify in the field by their weight relative to size and a reddish-brown streak test on unglazed porcelain. Commonly found in eroded sandstone areas or stream beds.