sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3-4 (Mohs scale), Color: White, tan, or gray, Luster: Dull to earthy, Crystal Structure: Hexagonal/Trigonal (as calcite), Cleavage: None (in rock form), SG: 2.3–2.7
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Physical properties
Hardness: 3-4 (Mohs scale), Color: White, tan, or gray, Luster: Dull to earthy, Crystal Structure: Hexagonal/Trigonal (as calcite), Cleavage: None (in rock form), SG: 2.3–2.7
Formation & geological history
Formed primarily in shallow, warm marine waters from the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from lake or ocean water.
Uses & applications
Extensively used in construction for aggregate, cement manufacture, building stone, and acid neutralization in soil and water treatment.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type in karst landscapes, leading to the formation of massive cave systems through dissolution by acidic groundwater.
Field identification & locations
Identify in the field by its tendency to effervesce (fizz) when in contact with dilute hydrochloric acid. It often contains visible fossils of marine organisms.
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