sedimentary
Sandstone Concretion
Ferruginous Sandstone Concretion
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
- Hardness
- 6-7 (if silica-rich)
- Color
- Tan, brown, ochre, rusty orange
- Luster
- Dull/Earthy
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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.
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