sedimentary
Oolite or Oolitic Limestone
Oolitic Limestone (Principal mineral: Calcite, CaCO3)
Hardness: 3-4 (Mohs scale), Color: Tan, beige, brown, or gray, Luster: Dull to earthy, Structure: Small spherical grains (ooliths) less than 2mm, Cleavage: None (rhombohedral for individual crystals)
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Physical properties
Hardness: 3-4 (Mohs scale), Color: Tan, beige, brown, or gray, Luster: Dull to earthy, Structure: Small spherical grains (ooliths) less than 2mm, Cleavage: None (rhombohedral for individual crystals)
Formation & geological history
Formed in warm, shallow, supersaturated marine waters. Ooliths grow as calcium carbonate precipitates around a sand grain or shell fragment nucleus while being agitated by wave action. Majority are from the Jurassic to Holocene periods.
Uses & applications
Used in construction as a dimension stone, decorative aggregate, lime production, and occasionally as a specimen for educational geology kits.
Geological facts
The word 'oolite' comes from the Greek word 'oion' for egg, describing its resemblance to fish roe. Much of the Florida Everglades and the Bahamian platform are underlain by oolitic limestone formations.
Field identification & locations
Identified by its 'fish roe' texture of tiny spheres. Can be tested with dilute HCl (will fizz). Found in sedimentary basins globally, commonly in areas like the UK (Portland Stone) and the Midwestern USA (Indiana Limestone).
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