sedimentary
Fossiliferous Limestone
Calcium Carbonate (CaCO3) with Bioclastic Inclusions
Hardness: 3-4 (Mohs scale); Color: Gray to dark gray matrix with white vocalized inclusions; Luster: Dull to earthy; Structure: Bioclastic/clastic; Cleavage: None (fractures irregularly); Specific gravity: 2.5-2.7
- Hardness
- 3-4 (Mohs scale)
- Color
- Gray to dark gray matrix with white vocalized inclusions
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: Gray to dark gray matrix with white vocalized inclusions; Luster: Dull to earthy; Structure: Bioclastic/clastic; Cleavage: None (fractures irregularly); Specific gravity: 2.5-2.7
Formation & geological history
Formed in shallow, warm marine environments through the accumulation of shell, coral, and algal debris. The pressure of overlying sediment causes lithification over millions of years, often dating from the Paleozoic or Mesozoic eras.
Uses & applications
Extensively used in construction as aggregate, in the manufacture of cement, as a decorative building stone, and for agricultural lime to neutralize soil acidity. Small specimens are popular for educational fossil collecting.
Geological facts
This specific specimen is a 'bioclast' or grainstone variety, containing fragments of ancient marine organisms such as crinoids, brachiopods, or bivalves. It acts as a natural carbon sink, storing atmospheric carbon dioxide for millions of years.
Field identification & locations
Identify by the presence of visible shell fragments or fossils within a fine-grained gray matrix. It will react and fizz (effervesce) when exposed to a drop of weak acid (like vinegar). Commonly found in former seabed regions such as the American Midwest or the UK.
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