sedimentary

Limestone

Sedimentary carbonate rock (CaCO3)

Hardness 3 on Mohs scale, grayish to brownish color, dull to earthy luster, microcrystalline or granular structure with poor cleavage.

Identified November 8, 2026More sedimentary →

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Physical properties

Hardness 3 on Mohs scale, grayish to brownish color, dull to earthy luster, microcrystalline or granular structure with poor cleavage.

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

Widely used in construction as crushed stone for road base, aggregate for concrete, and manufacturing Portland cement or agricultural lime.

Limestone frequently preserves fossils of ancient marine life and can dissolve over time to form spectacular cave systems and sinkholes.

Easily identified by its characteristic reaction to dilute hydrochloric acid, which produces carbon dioxide fizzing.

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)