sedimentary
Limestone
Carbonate rock (CaCO3)
AI-generated identification · may be incorrectMohs hardness: 3, Color: White to light grey, Luster: Dull to earthy, Structure: Fine-grained to crystalline, Composition: Mostly calcite and aragonite
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Physical properties
Mohs hardness: 3, Color: White to light grey, Luster: Dull to earthy, Structure: Fine-grained to crystalline, Composition: Mostly calcite and aragonite
Formation & geological history
Formed primarily from the accumulation of shell, coral, algal, and fecal debris in marine environments. It can also be formed by the precipitation of calcium carbonate from lake or ocean water.
Uses & applications
Extensively used in construction as an aggregate for road base and railroad ballast, in the manufacturing of cement/lime, and as a soil conditioner.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary building block of most of the world's pyramids and cathedrals.
Field identification & locations
Identifiable by its reaction to dilute hydrochloric acid (acid test), producing bubbles of CO2. Found globally in ancient seabed deposits.
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Other sedimentary specimens
Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion
Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image
fossil
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary