mineral

Weathered iron-rich geode or cavity fragment

Limonite/goethite-rich material, likely coating a weathered basaltic or volcanic host rock

AI-generated identification · may be incorrect

Rust-brown to yellow ochre, earthy to dull luster, porous and crumbly interior with a hard gray-brown rind; mainly amorphous or microcrystalline iron oxyhydroxides, typically Mohs 4–5.5, with no obvious cleavage.

Identified August 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed when iron-bearing minerals oxidized and hydrated in a vesicle or cavity of volcanic rock, producing limonite and goethite; likely a relatively young weathering product, commonly Quaternary or younger.

Uses & applications

Primarily a collector specimen and natural ochre pigment; iron oxides are also used industrially for pigments and minor iron ore, but this piece has little construction value.

Geological facts

The bright yellow-orange interior indicates hydrated iron oxides, while the dark rind may preserve the original volcanic host. Limonite is a field term rather than a single exact mineral.

Field identification & locations

Look for a yellow-brown streak, earthy texture, high density, and possible attraction if magnetite is present; distinguish it from sulfur, which is brighter yellow and softer. Common in weathered volcanic rocks, iron-rich soils, and hydrothermal cavities worldwide.