sedimentary
Limestone
Calcium Carbonate (CaCO3)
Mohs hardness of 3, colors range from white, gray, yellow to brown, dull to subvitreous luster, fine-grained to coarse crystal structure, good cleavage in three directions (rhombohedral), specific gravity of 2.71.
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Physical properties
Mohs hardness of 3, colors range from white, gray, yellow to brown, dull to subvitreous luster, fine-grained to coarse crystal structure, good cleavage in three directions (rhombohedral), specific gravity of 2.71.
Formation & geological history
Formed primarily from the accumulation of skeletal fragments of marine organisms such as coral, algal, and mollusks, or through chemical precipitation of calcium carbonate from water in shallow marine environments over millions of years.
Uses & applications
Extensively used in construction as building stone, as an aggregate for road bases, as a key ingredient in the manufacture of Portland cement, in agriculture to neutralize acidic soils, and in the production of lime.
Geological facts
Limestone often contains fossils of ancient marine life. Famous structures like the Great Pyramid of Giza and parts of the Empire State Building utilize limestone.
Field identification & locations
Easily identified in the field by its characteristic reaction to dilute hydrochloric acid, producing effervescence (fizzing). Found worldwide in sedimentary basins.
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