Limestone

Physical Properties

Hardness: 3-4 (Mohs), Color: Light gray to tan, Luster: Dull to earthy, Crystal structure: Hexagonal (trigonal) as calcite, Cleavage: Rhombohedral (though rarely visible in massive form), Specific gravity: 2.5-2.7

Formation & Geological History

Formed primarily in marine environments from the accumulation of calcium carbonate shells, corals, and skeletal remains or by chemical precipitation. Most abundant in sedimentary basins of various geological ages.

Uses & Applications

Extensively used in construction, agriculture (soil conditioning), the production of lime and cement, and as a dimension stone for architecture.

Geological Facts

Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. It is the primary type of stone found in caves and karst landscapes, often forming stalactites and stalagmites.

Field Identification & Locations

Can be identified in the field by its effervescence (bubbling) when a small amount of dilute acid like vinegar or HCl is applied. Often contains visible fossils or shell fragments. Commonly found in quarry environments or rocky outcrops.

Identified on: 5/3/2026

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