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.

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Quartz pebble

Silicon dioxide (SiO2)

Sedimentary Sandstone

Arenite (Sedimentary Rock)

Generic Pebble / Rock Fragment

Lithic fragment / Weathered rock

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)