sedimentary

Fossiliferous Limestone

Biogenic Sedimentary Rock (Calcite, CaCO3)

Hardness of 3 on the Mohs scale, tan to grey color, dull to earthy luster, and reacts strongly with hydrochloric acid.

Identified October 19, 2026More sedimentary →

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Physical properties

Hardness of 3 on the Mohs scale, tan to grey color, dull to earthy luster, and reacts strongly with hydrochloric acid.

Formed through the accumulation and cementation of skeletal fragments of marine organisms in shallow marine environments over millions of years.

Used primarily in the construction industry as crushed stone for road base, aggregate in concrete, and for manufacturing Portland cement.

Limestone often preserves ancient marine fossils like crinoids, brachiopods, and bryozoans, providing a clear record of past aquatic ecosystems.

Easily identified by its fossil content and characteristic fizz when tested with a weak acid; commonly found in sedimentary basins worldwide.

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)