Fossiliferous Limestone

Physical Properties

Hardness: 3-4 (Mohs scale); Color: Cream, tan, or grey; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite); Cleavage: Perfect rhombohedral in calcite, but usually not visible in bulk rock; Specific gravity: Approx 2.3-2.7.

Formation & Geological History

Formed in marine environments through the accumulation of shell fragments, coral, or other biological debris. Over millions of years, pressure and chemicals cement these fragments into rock. These often date to the Paleozoic or Mesozoic eras.

Uses & Applications

Used in construction as a building material, for manufacturing cement, as decorative stone, and as educational specimens for fossil collecting.

Geological Facts

Fossiliferous limestone is a primary source of information for paleontologists; it can contain intact organisms or fragmented shell hash (coquina). Most of the world's pyramids were built using limestone.

Field Identification & Locations

Identify in the field by looking for visible shell impressions or skeletal remains. It will react and fizz (effervesce) when exposed to a drop of weak acid (like vinegar or diluted HCl). Commonly found in areas that were ancient seabeds.

Identified on: 4/20/2026

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