sedimentary
Fossiliferous Limestone (Coquina)
Calcite (CaCO3) with Bioclastic inclusions
Hardness: 3 (Mohs scale), Color: Brown, tan, with white shell fragments, Luster: Dull/Earthy, Crystal Structure: Trigonal (microcrystalline matrix), Cleavage: Perfect rhombohedral in calcite matrix, Specific Gravity: 2.3 - 2.7
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Physical properties
Hardness: 3 (Mohs scale), Color: Brown, tan, with white shell fragments, Luster: Dull/Earthy, Crystal Structure: Trigonal (microcrystalline matrix), Cleavage: Perfect rhombohedral in calcite matrix, Specific Gravity: 2.3 - 2.7
Formation & geological history
Forms in shallow marine environments from the accumulation of organic remains such as shells, corals, and algae. Over millions of years, pressure and minerals cement these fragments into rock.
Uses & applications
Used primarily in construction (aggregate), cement manufacturing, architecture, and as a decorative stone in landscaping or for fossil collecting.
Geological facts
Fossiliferous limestone provides a record of past biodiversity; some specimens contain perfectly preserved fossils of extinct species millions of years old.
Field identification & locations
Identify by looking for visible shell fragments or fossils embedded in a soft, earthy matrix. It will react and fizz if exposed to weak acid (dilute HCl or vinegar). Commonly found in ancient sea beds.
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