sedimentary

Sandstone Concretion

Clastic Sedimentary Concretion (typically Quartz/Silica with Iron Oxide)

Hardness: 6-7 (Mohs scale largely depends on cement/quartz content); Color: Reddish-brown, tan, or ochre; Luster: Dull, earthy; Crystal structure: Granular/Microcrystalline; Cleavage: None; Specific gravity: Approx 2.0-2.6.

Hardness: 6-7 (Mohs scale largely depends on cement/quartz content)
Color: Reddish-brown, tan, or ochre
Luster: Dull, earthy

Identified April 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the precipitation of mineral cement within the spaces between sediment grains. These often form early in the burial history of a sediment layer, growing outward from a nucleus. The reddish color indicates iron oxide (hematite/limonite) staining.

Uses & applications

Primarily used for geological study, landscaping, and as curios for collectors due to their unusual 'sculpted' shapes.

Geological facts

Concretions are often mistaken for fossils, meteorites, or man-made artifacts because of their odd, bulbous, or symmetrical shapes. Some famous examples include the Moeraki Boulders in New Zealand.

Field identification & locations

Identify in the field by their rounded or irregular nodular shapes that differ from the surrounding bedding planes. Common in arid environments or exposed riverbanks with sedimentary outcrops.

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