sedimentary

Sandstone Cobble

Arenite (primarily SiO2)

Mohs hardness 6-7, dull earthy luster, gritty texture, brownish-grey color, composed mostly of quartz grains.

Identified October 31, 2026More sedimentary →

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Physical properties

Mohs hardness 6-7, dull earthy luster, gritty texture, brownish-grey color, composed mostly of quartz grains.

Formed by the compaction and cementation of mineral particles or rock fragments, subsequently rounded by fluvial or glacial transport.

Commonly used as construction aggregate, landscaping stone, and occasionally historical building material.

Its rounded rectangular shape is typically the result of natural jointing in bedded layers followed by abrasive water or glacial erosion.

Identified in the field by its sandpaper-like tactile feel, clastic grain structure, and resistance to effervescence in acid.

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

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)