Sedimentary

Sandstone Concretion

Sedimentary concretion

Hardness varies (typically 6-7 if quartz-rich), brownish/tan/reddish color from iron oxides, dull luster, composed of cemented sand grains, high specific gravity compared to surrounding rock.

Identified April 26, 2026More sedimentary →

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Physical properties

Hardness varies (typically 6-7 if quartz-rich), brownish/tan/reddish color from iron oxides, dull luster, composed of cemented sand grains, high specific gravity compared to surrounding rock.

Formation & geological history

Formed by the precipitation of mineral cement (often calcite, iron oxide, or silica) around a nucleus in sedimentary rock, gradually growing outward in a spherical or subspherical shape over geological time.

Uses & applications

Collectibles, garden ornaments, educational specimens. Rarely used in industry.

Geological facts

Concretions are often mistaken for fossilized eggs, meteorites, or human-made artifacts due to their unusually perfect spherical shape.

Field identification & locations

Identify by their spherical shape and composition similar to the host rock but harder. Often found weathering out of sedimentary cliffs, bluffs, or stream beds.