sedimentary

Limonite/Goethite Concretion

Goethite (FeO(OH))

Hardness: 5-5.5; Color: Dark brown to ochre; Luster: Dull/Earthy; Structure: Massive or botryoidal; Gravity: 3.3-4.3

Identified July 14, 2026More sedimentary →

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Physical properties

Hardness: 5-5.5; Color: Dark brown to ochre; Luster: Dull/Earthy; Structure: Massive or botryoidal; Gravity: 3.3-4.3

Formed as a chemical precipitate from weathering of iron-rich minerals in soil and sedimentary layers.

Historical iron ore, source of brown/yellow pigments (ochre), and collected as mineral specimens.

Commonly known as 'bog iron,' it was a primary source of iron for various cultures before high-yield mining became common.

Identify by its dark brown color and yellow-brown streak test. Frequently found in stream beds or weathered soil zones.

Sandstone or Siltstone

Arenite (if sandstone)

Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

Shale

Shale (clastic sedimentary rock)

Brown Sandstone (River Rock)

Arenite

Mudstone

Argillite / Siliciclastic sedimentary rock

Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)