sedimentary
Limestone (Fossiliferous)
Calcium Carbonate (CaCO3) - Bioclastic Limestone
Hardness: 3 (Mohs scale), Color: light grey to tan, Luster: dull/earthy, Crystal Structure: Trigonal (microcrystalline calcite), Cleavage: None in rock form, Specific Gravity: 2.5-2.7
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Physical properties
Hardness: 3 (Mohs scale), Color: light grey to tan, Luster: dull/earthy, Crystal Structure: Trigonal (microcrystalline calcite), Cleavage: None in rock form, Specific Gravity: 2.5-2.7
Formation & geological history
Formed in shallow marine environments through the accumulation of organic debris such as coral, shells, and algae. Commonly dates from the Paleozoic to Mesozoic eras.
Uses & applications
Used primarily in the construction industry as building stone, road base, and a key ingredient in cement. Also used in soil neutralization in agriculture.
Geological facts
Limestone accounts for about 10% of the total volume of all sedimentary rocks globally. Fossiliferous limestone often contains perfectly preserved skeletons of ancient marine life like crinoids or brachiopods.
Field identification & locations
Identify in the field by its reaction (fizzing) when exposed to a weak acid like vinegar. Look for visible shell fragments or small pore-like structures. Found commonly in areas that were ancient seabed, such as the Midwestern United States.
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