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.

Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion

Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)