sedimentary
Limestone (fossiliferous or weathered)
Sedimentary carbonate rock primarily composed of calcium carbonate (CaCO3)
AI-generated identification · may be incorrectHardness of 3 on the Mohs scale, color ranges from yellowish-brown, tan, to gray, luster is earthy to dull, crystal structure is microcrystalline or cryptocrystalline (calcite), cleavage is rhombohedral in pure calcite crystals but generally absent in massive rock form, specific gravity around 2.7.
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Physical properties
Hardness of 3 on the Mohs scale, color ranges from yellowish-brown, tan, to gray, luster is earthy to dull, crystal structure is microcrystalline or cryptocrystalline (calcite), cleavage is rhombohedral in pure calcite crystals but generally absent in massive rock form, specific gravity around 2.7.
Formation & geological history
Formed through the accumulation of skeletal fragments of marine organisms such as coral, algal, and foraminifera, or through chemical precipitation of calcium carbonate from water in shallow marine environments.
Uses & applications
Widely used in the construction industry for crushed stone in road base, production of cement, agriculture as soil conditioner, and in various chemical and industrial applications.
Geological facts
Limestone can dissolve slightly in acidic water, leading to the formation of spectacular cave systems, stalactites, and sinkholes over geological time scales.
Field identification & locations
Can be easily identified by its characteristic fizz or effervescence when a drop of weak hydrochloric acid (or vinegar) is applied to its surface. Found worldwide in regions with ancient marine depositional histories.
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