sedimentary

Fossiliferous Limestone

Biogenic Limestone (Calcium Carbonate, CaCO3)

AI-generated identification · may be incorrect

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

Identified July 7, 2026More sedimentary →

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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.