sedimentary
Limestone
Sedimentary rock composed mainly of calcite (CaCO3)
Mohs hardness of 3; dull to earthy luster; light tan, beige, grey, or yellowish color; fine-grained texture; fizzes vigorously when exposed to dilute hydrochloric acid.
Identified More sedimentary →
Explore Limestone in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Mohs hardness of 3; dull to earthy luster; light tan, beige, grey, or yellowish color; fine-grained texture; fizzes vigorously when exposed to dilute hydrochloric acid.
Formation & geological history
Formed primarily in shallow, warm marine environments through the accumulation and compaction of organic debris like shells, coral, and micro-fossils, as well as chemical precipitation of calcium carbonate over millions of years.
Uses & applications
Extensively used in construction, cement manufacturing, road base, soil treatment in agriculture, building stone, and lime production.
Geological facts
Limestone forms many famous natural landscapes, including karst topographies with dramatic caves, sinkholes, and towers. It constitutes about 10% of the total volume of all sedimentary rocks.
Field identification & locations
Can be easily identified by its soft surface (scratched by a copper penny or steel nail) and its strong reactivity (effervescence) with acid. Extremely common worldwide in ancient marine sedimentary basins.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale
Argillaceous sedimentary rock
sedimentary
Mudstone
Argillite / Siliciclastic sedimentary rock
sedimentary