sedimentary
Fossiliferous Limestone
Biogenic Limestone (Calcium Carbonate, CaCO3)
Hardness: 3-4 (Mohs scale); Color: Gray to tan; Luster: Dull/Earthy; Structure: Clastic or organic; contains visible shell fragments and crinoid/brachiopod outlines.
- Hardness
- 3-4 (Mohs scale)
- Color
- Gray to tan
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: Gray to tan; Luster: Dull/Earthy; Structure: Clastic or organic; contains visible shell fragments and crinoid/brachiopod outlines.
Formation & geological history
Formed in warm, shallow marine environments from the accumulation of calcium carbonate and biological remains like shells and corals, often dating back hundreds of millions of years (Paleozoic or Mesozoic Eras).
Uses & applications
Used in the manufacturing of cement, as a building stone, in road base construction, and as a popular specimen for educational fossil collecting.
Geological facts
This specimen is a 'river rock' or 'cobble' that has been smoothed by water erosion, revealing cross-sections of ancient marine fossils embedded in the matrix. Limestone makes up about 10% of the total volume of all sedimentary rocks.
Field identification & locations
Identify by looking for circular or crescent-shaped white inclusions (fossil cross-sections) in a fine-grained gray matrix. It will fizz when exposed to weak acid (like vinegar). Commonly found in riverbeds and coastal areas.
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