sedimentary
Limestone
Calcium Carbonate (CaCO3)
Mohs hardness of 3, light beige to grey earthy color, dull to earthy luster, massive or fine-grained texture, perfect rhombohedral cleavage when visible, effervesces strongly in dilute hydrochloric acid.
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Physical properties
Mohs hardness of 3, light beige to grey earthy color, dull to earthy luster, massive or fine-grained texture, perfect rhombohedral cleavage when visible, effervesces strongly in dilute hydrochloric acid.
Formation & geological history
Formed in warm, shallow marine environments through the accumulation and compaction of organic debris like shells, coral, and algal remains, or by chemical precipitation of calcium carbonate from water.
Uses & applications
Extensively used as construction aggregate, crushed stone for road bases, a primary ingredient in cement and concrete manufacturing, soil conditioner in agriculture, and chemical lime production.
Geological facts
Limestone covers about 10% of the total volume of all sedimentary rocks on Earth. Acidic groundwater easily dissolves limestone, leading to the formation of extensive cave systems, sinkholes, and karst landscapes.
Field identification & locations
Identify in the field by its softness (can be scratched with a steel nail) and positive acid test (fizzes with acid). Extremely common worldwide in sedimentary rock sequences and quarries.
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