sedimentary
Limestone
Calcium Carbonate (CaCO3)
Hardness: 3 on the Mohs scale, Color: White, gray, tan, yellow, or brown, Luster: Earthy to dull, Crystal structure: Trigonal (as calcite), Cleavage: Perfect rhombohedral cleavage, Specific Gravity: 2.7 - 2.9
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Physical properties
Hardness: 3 on the Mohs scale, Color: White, gray, tan, yellow, or brown, Luster: Earthy to dull, Crystal structure: Trigonal (as calcite), Cleavage: Perfect rhombohedral cleavage, Specific Gravity: 2.7 - 2.9
Formation & geological history
Formed in shallow marine environments over millions of years through the accumulation of shell, coral, algal, and fecal debris, often ranging from Paleozoic to Cenozoic eras.
Uses & applications
Widely used in construction (as building stone, crushed stone for road base, and a primary ingredient in Portland cement), agriculture (soil conditioning), and metallurgy.
Geological facts
Limestone is famous for forming spectacular cave systems and karst landscapes through chemical weathering by slightly acidic groundwater.
Field identification & locations
Easily identified by its reaction with dilute hydrochloric acid, which causes it to effervesce (fizz) due to the release of carbon dioxide gas. Commonly found in sedimentary basins worldwide.
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