sedimentary
Limestone
Limestone (Calcium Carbonate - CaCO3)
Hardness: 3-4 (Mohs scale), Color: tan, grey, or yellowish, Luster: dull to earthy, Cleavage: poor (brittle fracture), Specific Gravity: 2.3 - 2.7, Grain: fine to medium grained with visible clastic fragments.
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Physical properties
Hardness: 3-4 (Mohs scale), Color: tan, grey, or yellowish, Luster: dull to earthy, Cleavage: poor (brittle fracture), Specific Gravity: 2.3 - 2.7, Grain: fine to medium grained with visible clastic fragments.
Formation & geological history
Formed primarily in shallow marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from calcium-rich waters.
Uses & applications
Used extensively in construction as aggregate, for making cement, as a flux in steel production, and as a soil conditioner in agriculture.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type found in karst landscapes where caves and sinkholes are common.
Field identification & locations
Identify in the field by its reaction to dilute hydrochloric acid (it will fizz or effervesce). Look for fossils or a gritty, sandy texture. Common globally, especially in areas previously covered by ancient seas.
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