sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3-4 (Mohs), Color: Light gray/white/cream, Luster: Dull to earthy, Crystal Structure: Trigonal (Microcrystalline), Cleavage: Perfect rhombohedral in calcite crystals, SG: 2.7
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Physical properties
Hardness: 3-4 (Mohs), Color: Light gray/white/cream, Luster: Dull to earthy, Crystal Structure: Trigonal (Microcrystalline), Cleavage: Perfect rhombohedral in calcite crystals, SG: 2.7
Formation & geological history
Formed in marine environments through the accumulation of organic debris such as shell, coral, and algal material, or by chemical precipitation. Can date from the Precambrian to Cenozoic eras.
Uses & applications
Used primarily in construction for building stone, road base, and as a raw material in cement and lime production. Also used as a soil conditioner in agriculture.
Geological facts
Limestone occupies about 10% of the total volume of all sedimentary rocks. It is the primary rock type that forms karst topography, featuring caves and sinkholes due to its solubility in acid.
Field identification & locations
Identify in the field by its light color and a positive fizz test when in contact with dilute hydrochloric acid. Commonly found in riverbeds, cliffs, and quarries globally.
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