sedimentary
Fossiliferous Limestone
Biogenic Limestone (CaCO3)
Hardness: 3-4 (Mohs); Color: Pinkish-red to brownish matrix with white clasts; Luster: Dull to earthy; Structure: Fragmental/Clastic; Cleavage: None (conchoidal fracture).
- Hardness
- 3-4 (Mohs)
- Color
- Pinkish-red to brownish matrix with white clasts
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (Mohs); Color: Pinkish-red to brownish matrix with white clasts; Luster: Dull to earthy; Structure: Fragmental/Clastic; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed in warm, shallow marine environments from the accumulation of calcium carbonate and organic debris (shell/coral fragments). This specimen appears to contain crinoid or shell fragments in a hematite-stained calcitic matrix.
Uses & applications
Primarily used in construction (crushed stone, cement), architectural cladding, and as a decorative garden rock or collector's specimen.
Geological facts
The reddish color is often caused by trace amounts of iron oxide (hematite) during diagenesis. It acts as a biological record of ancient marine life.
Field identification & locations
Identify by testing for a reaction (fizzing) with dilute hydrochloric acid. Look for visible fossil fragments or bioclasts within the matrix. Commonly found in ancient inland sea beds.
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