Rock Identifier
Limestone (Sedimentary Rock (Primarily Calcium Carbonate, CaCO3)) — sedimentary
sedimentary

Limestone

Sedimentary Rock (Primarily Calcium Carbonate, CaCO3)

Hardness: 3 on the Mohs scale. Color: Typically gray, white, tan, or yellowish. Luster: Earthy to dull. Crystal structure: Microcrystalline or amorphous matrix of calcite. Cleavage: Not generally applicable to the bulk rock (calcite has rhombohedral cleavage). Specific gravity: 2.7 - 2.9.

Hardness
3 on the Mohs scale
Color
Typically gray, white, tan, or yellowish
Luster
Earthy to dull
Identified More sedimentary →
Explore Limestone in the encyclopedia →

Identify your own rocks.

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

App StoreGoogle Play

Physical properties

Hardness: 3 on the Mohs scale. Color: Typically gray, white, tan, or yellowish. Luster: Earthy to dull. Crystal structure: Microcrystalline or amorphous matrix of calcite. Cleavage: Not generally applicable to the bulk rock (calcite has rhombohedral cleavage). Specific gravity: 2.7 - 2.9.

Formation & geological history

Formed in shallow marine environments through the accumulation of shell, coral, algal, and fecal debris, or by the chemical precipitation of calcium carbonate from water. Geologic age ranges from Precambrian to recent.

Uses & applications

Extensively used in the construction industry as building stone, aggregate in concrete, road base, and in the production of Portland cement and agricultural lime.

Geological facts

Limestone often contains well-preserved fossils of ancient marine life. Famous examples include the Great Pyramid of Giza, which is constructed largely of limestone blocks.

Field identification & locations

Can be easily identified in the field by its characteristic gray or tan color and strong effervescence (fizzing) when a drop of dilute hydrochloric acid is applied due to the release of carbon dioxide gas. Found worldwide in sedimentary basins.

More like this

Other sedimentary specimens

Sandstone or Siltstone (Arenite (if sandstone)) — Sedimentary

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary
Sedimentary Sandstone (Arenite (Sedimentary Rock)) — sedimentary

Sedimentary Sandstone

Arenite (Sedimentary Rock)

sedimentary
Fossiliferous Concretion (Septarian Concretion containing Brachiopods/Crinoids) — fossil

Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

fossil
Banded Siltstone / Mudstone Pebble (Siltstone / Argillite) — sedimentary

Banded Siltstone / Mudstone Pebble

Siltstone / Argillite

sedimentary
Shale (or Mudstone/Siltstone) (Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)) — sedimentary

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)

sedimentary
Shale (Shale (clastic sedimentary rock)) — sedimentary

Shale

Shale (clastic sedimentary rock)

sedimentary