sedimentary

Fossiliferous Limestone (Coral Fossil)

Calcium Carbonate (CaCO3) with Colonial Coral inclusions

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs); Color: Grey, white, or tan with dark lichen spots; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline calcite); Cleavage: Perfect rhombohedral in calcite matrix.

Hardness: 3-4 (Mohs)
Color: Grey, white, or tan with dark lichen spots
Luster: Dull to earthy

Identified June 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in warm, shallow marine environments through the accumulation of calcium carbonate and the skeletal remains of coral colonies. Most frequently dates to the Paleozoic or Mesozoic eras (often hundreds of millions of years old).

Uses & applications

Primarily used as a decorative specimen for collectors. Industrial limestone is used in cement, construction, and agriculture; polished slabs are used in architecture.

Geological facts

The honeycomb pattern visible on the surface is the fossilized structure of a coral colony. These rocks provide critical data to geologists about ancient sea levels and prehistoric climates.

Field identification & locations

Identify in the field by looking for repetitive geometric or 'honeycomb' patterns on weathered limestone surfaces. It will react (fizz) when exposed to a weak acid like vinegar. Commonly found in areas that were once prehistoric seabeds.