sedimentary

Crushed Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Gray to dark gray; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral in calcite crystals, but usually presents as irregular fracture in rock mass; Specific gravity: 2.5-2.7

Hardness: 3 on Mohs scale
Color: Gray to dark gray
Luster: Dull to earthy

Identified June 24, 2026More sedimentary →

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Physical properties

Formation & geological history

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

Uses & applications

Extensively used in construction as road base, concrete aggregate, and railroad ballast. Also used as a flux in steel making, a soil conditioner in agriculture, and in the production of cement and lime.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It often contains fossils of ancient marine organisms, providing an important record of biological history.

Field identification & locations

Identify in the field by its gray color and the 'fizz test' (it reacts and bubbles when exposed to dilute hydrochloric acid). Commonly found in thick bedding planes in sedimentary basins worldwide.