sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 (Mohs Scale), Color: tan/light gray, Luster: dull to earthy, Crystal Structure: Hexagonal (as calcite), Cleavage: Perfect rhombohedral in crystal form, Specific Gravity: 2.7
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Physical properties
Hardness: 3 (Mohs Scale), Color: tan/light gray, Luster: dull to earthy, Crystal Structure: Hexagonal (as calcite), Cleavage: Perfect rhombohedral in crystal form, Specific Gravity: 2.7
Formation & geological history
Formed primarily from the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. Can also form through chemical precipitation from lakewater or ocean water.
Uses & applications
Used extensively in construction (road base, concrete, mortar), agriculture to neutralize soil acidity, and as a raw material for cement.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type found in 'Karst' topography, which is known for caves and sinkholes.
Field identification & locations
Identify in the field using a drop of weak acid (like vinegar); it will effervesce (fizz). Commonly found in areas that were once prehistoric seafloors.
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