sedimentary
Limestone (with weathering rind)
Calcium Carbonate (CaCO3)
Mohs hardness 3, earthy to dull luster, grayish-tan color with a buff-yellow weathered exterior crust, fine-grained microcrystalline texture, effervesces strongly in dilute hydrochloric acid.
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Physical properties
Mohs hardness 3, earthy to dull luster, grayish-tan color with a buff-yellow weathered exterior crust, fine-grained microcrystalline texture, effervesces strongly in dilute hydrochloric acid.
Formation & geological history
Formed primarily in shallow, calm, warm marine environments through the accumulation and compaction of organic debris such as shell fragments and corals, as well as chemical precipitation of calcite.
Uses & applications
Widely used as crushed stone for road construction, production of cement and lime, soil conditioner in agriculture, and building stone.
Geological facts
Limestone accounts for about 10% of the total volume of all sedimentary rocks. Caves and karst landscapes around the world form almost exclusively in limestone deposits dissolved by acidic groundwater over geological time.
Field identification & locations
Can be identified in the field by testing its hardness (scratched easily with a steel nail) and checking for a reaction (fizzing) when exposed to a weak acid. Commonly found in former inland sea beds, quarry exposures, and river valleys worldwide.
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