sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness 3 on the Mohs scale, colors range from white to gray and tan, dull to sub-earthy luster, fine-grained amorphous or crystalline structure.

Identified October 18, 2026More sedimentary →

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Physical properties

Hardness 3 on the Mohs scale, colors range from white to gray and tan, dull to sub-earthy luster, fine-grained amorphous or crystalline structure.

Formed from the accumulation of skeletal fragments, coral, algal, and fecal debris in shallow marine environments over millions of years.

Widely used in construction as building stone, aggregate in concrete, and for manufacturing cement and agricultural lime.

Limestone often contains well-preserved fossils of ancient marine organisms and dissolves slowly in acidic water to form karst landscapes and caves.

Easily identified by its characteristic fizz when tested with dilute hydrochloric acid; found globally in sedimentary basins.

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)