sedimentary

Calcite Vein on Limestone

Calcium Carbonate (CaCO3)

Mohs hardness 3, white to translucent color, vitreous to earthy luster, trigonal crystal system, and perfect rhombohedral cleavage.

Identified October 18, 2026More sedimentary →

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Physical properties

Mohs hardness 3, white to translucent color, vitreous to earthy luster, trigonal crystal system, and perfect rhombohedral cleavage.

Formed through the precipitation of calcium carbonate from mineral-rich hydrothermal or groundwater solutions filling fractures in host rock.

Used widely in construction materials, agricultural soil treatment, and chemical manufacturing, as well as valued by mineral collectors.

Calcite is the primary constituent of limestone and marble and exhibits strong effervescence when exposed to dilute hydrochloric acid.

Identified easily by its low hardness (easily scratched by a coin) and positive acid test, commonly found in sedimentary environments 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)