sedimentary
Fossiliferous limestone
Bioclastic limestone, primarily calcite (CaCO₃)
AI-generated identification · may be incorrectUsually Mohs 3, pale gray to beige, dull to weakly pearly; fine-grained matrix with visible shell or skeletal fragments and irregular bedding. Calcite commonly fizzes vigorously with dilute hydrochloric acid.
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Physical properties
Usually Mohs 3, pale gray to beige, dull to weakly pearly; fine-grained matrix with visible shell or skeletal fragments and irregular bedding. Calcite commonly fizzes vigorously with dilute hydrochloric acid.
Formation & geological history
Forms from accumulated marine shells, skeletal debris, and lime mud that lithify into carbonate rock, commonly in Paleozoic–Mesozoic shallow-marine environments. The specimen appears weathered and may preserve fragmentary fossil textures.
Uses & applications
Used as aggregate, cement and lime feedstock, building stone, and educational or decorative specimens; fossil-bearing pieces have modest collecting value.
Geological facts
Calcite-rich limestone can recrystallize into marble during metamorphism, destroying much fossil detail. Fossil identification requires close examination of diagnostic structures or a polished/cut surface.
Field identification & locations
Look for embedded shell shapes, bedding, porous weathered surfaces, and acid effervescence; common worldwide in former shallow seas. Avoid damaging potentially important fossils with acid testing.
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