sedimentary

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Gray, tan, or buff; Luster: Dull to earthy; Structure: Often contains visible fossil fragments or small pits; Specific Gravity: 2.5-2.7

Hardness: 3 on Mohs scale
Color: Gray, tan, or buff
Luster: Dull to earthy

Identified June 4, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Gray, tan, or buff; Luster: Dull to earthy; Structure: Often contains visible fossil fragments or small pits; Specific Gravity: 2.5-2.7

Formation & geological history

Formed in marine environments through the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from lake or ocean water. Most visible deposits vary from Paleozoic to Cenozoic eras.

Uses & applications

Extensively used in construction as aggregate, in cement manufacturing, for soil treatment in agriculture, and as a dimension stone for architecture.

Geological facts

Limestone is the primary rock type found in karst landscapes, which are characterized by caves, sinkholes, and underground drainage systems. About 10% of all sedimentary rocks are limestones.

Field identification & locations

Identified in the field by its softness (can be scratched by a copper coin) and its strong effervescence when exposed to a weak acid like vinegar or HCl. Found globally in areas that were once prehistoric seafloors.