sedimentary

Limonite (Ochreous Sandstone)

Hydrous ferric oxides (FeO(OH)qnH2O)

Hardness: 1-5 (variable), Color: yellow-brown to mustard-orange, Luster: dull/earthy, Crystal system: amorphous, Texture: granular and friable.

Identified July 8, 2026More sedimentary →

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Physical properties

Hardness: 1-5 (variable), Color: yellow-brown to mustard-orange, Luster: dull/earthy, Crystal system: amorphous, Texture: granular and friable.

Formed by the oxidation and hydration of iron-rich minerals in sedimentary environments. Common in bog deposits and as a staining agent in sandstone.

Used historically as a pigment (ochre), a low-grade iron ore, and as a natural dye. Collectors value it for its vibrant earthy colors.

Limonite is naturally occurring rust. It has been used by humans for cave paintings for at least 30,000 years due to its permanence as a pigment.

Identified by its distinctive yellowish-brown streak and earthy smell when wet. Found commonly in weathered sedimentary rock outcrops worldwide.

Sandstone or Siltstone

Arenite (if sandstone)

Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

Chert Breccia

Brecciated Chert (Microcrystalline Silica)

Shale or Slaty Mudstone

Argillaceous sedimentary rock

Sandstone

Arenite (primarily SiO2)