sedimentary
Fossiliferous Limestone (Coral Fossil)
Calcium Carbonate (CaCO3) with Colonial Coral inclusions
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 More sedimentary →
Explore Fossiliferous Limestone (Coral Fossil) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
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.
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.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary