sedimentary
Limestone (with possible Crinoid or Fossil Impression)
Calcium Carbonate (CaCO3) / Calcite
AI-generated identification · may be incorrectMohs hardness of 3, off-white to pale tan color, dull/earthy luster, fine-grained microcrystalline structure, effervesces vigorously in weak acid.
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Physical properties
Mohs hardness of 3, off-white to pale tan color, dull/earthy luster, fine-grained microcrystalline structure, effervesces vigorously in weak acid.
Formation & geological history
Formed through the accumulation and compaction of organic marine debris, calcium carbonate shells, and micro-organisms in shallow marine environments over millions of years.
Uses & applications
Widely used as building stone, concrete aggregate, lime production, soil acidity regulation, and industrial fluxing agent.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth and often preserves delicate ancient marine life fossils like crinoids, brachiopods, and corals.
Field identification & locations
Identified by its softness (scratched easily with a steel knife), dull chalky texture, and effervescence with diluted hydrochloric acid. Commonly found in sedimentary basins and ancient seabed deposits worldwide.
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