sedimentary
Limestone
Calcium Carbonate (CaCO3)
Mohs hardness of 3, typically gray, white, or tan in color, dull to earthy luster, fine-grained to coarse-grained crystal structure, good cleavage in three directions, specific gravity around 2.7
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Physical properties
Mohs hardness of 3, typically gray, white, or tan in color, dull to earthy luster, fine-grained to coarse-grained crystal structure, good cleavage in three directions, specific gravity around 2.7
Formation & geological history
Formed by the accumulation of organic remains such as shells and coral, or through the chemical precipitation of calcium carbonate from water in marine environments
Uses & applications
Widely used in construction (as building blocks, crushed stone for road base, and a primary ingredient in Portland cement), agriculture (for soil neutralization), and industrial manufacturing
Geological facts
Limestone often contains fossils of ancient marine organisms and is prone to dissolution by slightly acidic groundwater, creating impressive cave systems and karst topography
Field identification & locations
Easily identified in the field by its characteristic effervescence (fizzing) when a drop of dilute hydrochloric acid is applied, due to the release of carbon dioxide
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