sedimentary

Sandstone Concretion

Quartz sandstone concretion (SiO2)

Hardness of 6-7 on the Mohs scale, brownish-red color, dull to earthy luster, and fine-grained clastic structure.

Identified November 12, 2026More sedimentary →

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Physical properties

Hardness of 6-7 on the Mohs scale, brownish-red color, dull to earthy luster, and fine-grained clastic structure.

Formed through the cementation of sand grains by mineral precipitation in subsurface groundwater over millions of years.

Primarily collected as a geological curiosity or display specimen due to its unusual weathering shapes.

Differential weathering often causes these masses to erode into bizarre, sculptural shapes that frequently mimic carved artifacts or fossils.

Found globally in sedimentary rock formations, easily identified by its distinct rounded protrusions and quartz composition.

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

Sandstone or Siltstone

Arenite (if sandstone)

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)