sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale), Color: light grey to tan, Luster: dull to earthy, Crystal structure: Trigonal (as calcite), Cleavage: Rhombohedral (in mineral form), Specific gravity: 2.3-2.7

Identified July 21, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale), Color: light grey to tan, Luster: dull to earthy, Crystal structure: Trigonal (as calcite), Cleavage: Rhombohedral (in mineral form), Specific gravity: 2.3-2.7

Formation & geological history

Formed in marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also be formed by the chemical precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Used primarily in construction for building stone, road base, and as a raw material in the manufacture of cement and lime.

Geological facts

Limestone accounts for about 10% of the total volume of all sedimentary rocks. It is the primary rock type found in karst landscapes and often contains well-preserved fossils.

Field identification & locations

Can be identified in the field by its softness (scratched by a copper penny) and its reaction to dilute hydrochloric acid (effervescence). Highly common in areas with ancient seabed exposure.