sedimentary

Fossiliferous Limestone

Calcium Carbonate (CaCO3) with Bioclasts

Hardness: 3 (Mohs scale); Color: Light gray to blue-gray; Luster: Dull to earthy; Structure: Granular with visible fossil imprints; Cleavage: None (conchoidal to irregular fracture); Specific Gravity: 2.5-2.7

Hardness: 3 (Mohs scale)
Color: Light gray to blue-gray
Luster: Dull to earthy

Identified June 3, 2026More sedimentary →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed in warm, shallow marine environments from the accumulation of shell, coral, algal, and fecal debris. These sediments are lithified over millions of years through compaction and cementation. Often dates from the Paleozoic or Mesozoic eras.

Uses & applications

Used primarily in the construction industry as crushed stone for road base, concrete aggregate, and the production of cement and lime. It is also used as an agricultural soil conditioner.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. When it contains high concentrations of recognizable fossils, it provides a crucial record of ancient marine life and past climate conditions.

Field identification & locations

Identify in the field by its characteristic gray color and the presence of small shell or organic remains. A definitive test is the 'acid test': it will effervesce (fizz) vigorously when a drop of dilute hydrochloric acid or vinegar is applied. Found worldwide in regions once covered by inland seas.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Sandstone

Arenite (primarily SiO2)

sedimentary

Chert Breccia

Brecciated Chert (Microcrystalline Silica)

sedimentary

Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary

Sandstone

Arenite

sedimentary