Sandstone Concretion

Physical Properties

Hardness: 6-7 (if silica-rich); Color: Tan, brown, ochre, rusty orange; Luster: Dull/Earthy; Structure: Spherical or discoid mass; Cleavage: None; Specific Gravity: 2.0-2.6

Formation & Geological History

Formed by the precipitation of mineral cement within the spaces between sediment grains (often around a nucleus like a shell or leaf fragment) during diagenesis in sedimentary basins.

Uses & Applications

Primarily of geological and educational interest for collectors; sometimes used as garden decoration or landscape stones.

Geological Facts

Concretions are often mistaken for fossils, eggs, or meteorites due to their unusually symmetric shapes. They can range in size from tiny marbles to boulders several meters in diameter.

Field Identification & Locations

Identify by its rounded, distinct shape that differs from the surrounding rock layers. Often found weathering out of softer sandstone or shale cliffs. Check for concentric internal layers if broken.

Identified on: 4/14/2026

Mode: Standard