Fossiliferous Limestone with Brachiopod shell

Physical Properties

Hardness: 3 (Mohs scale), Color: Creamish-white to light gray, Luster: Dull to earthy (matrix) with vitreous fossil imprints, Crystal structure: Orthorhombic or Trigonal, Cleavage: Perfect rhombohedral in calcite crystals, SG: 2.7

Formation & Geological History

Formed through the accumulation of organic debris such as shells, coral, and algal remains in shallow, warm marine environments. Often dates from the Paleozoic to Mesozoic eras.

Uses & Applications

Used primarily for geological education, fossil collecting, and occasionally as a source of lime or in construction. This specific small sample is mainly a collector's item.

Geological Facts

Limestone covers about 10 percent of the total land area of the Earth. The fossils within it are valuable indicators of past climate and environmental conditions.

Field Identification & Locations

Identify by looking for shell imprints or rib-like structures (brachiopod hinges) in a soft, easily scratched matrix that fizzles when exposed to weak acid (HCl). Found globally in sedimentary basins.

Identified on: 5/3/2026

Mode: Standard