sedimentary

Fossiliferous Limestone (Crinoidal)

Calcium Carbonate (CaCO3) - Limestone containing bioclasts

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale); Color: Gray, tan, or off-white; Luster: Dull to earthy; Texture: Coarse-grained with visible fossil fragments; Cleavage: None (fractures irregularly); Specific gravity: 2.3–2.7

Hardness: 3-4 (Mohs scale)
Color: Gray, tan, or off-white
Luster: Dull to earthy

Identified March 17, 2026More sedimentary →

Explore Fossiliferous Limestone (Crinoidal) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed in warm, shallow marine environments by the accumulation of organic debris such as shell, coral, and algal fragments. These specific specimens often date from the Paleozoic era (approx. 250–540 million years ago) cemented by calcium carbonate precipitation.

Uses & applications

Used in the construction industry as aggregate, cement production, and building stone. Highly polished slabs are used for architectural cladding. Collectors value them for the visible ancient marine life they contain.

Geological facts

This specimen contains fragments of crinoids, often called 'sea lilies,' which are marine animals related to starfish. Some crinoid-rich limestones are so dense with fossils that they are referred to as 'encrinites.'

Field identification & locations

Identify in the field by looking for circular or star-shaped cross-sections of fossil stems and a rapid effervescence (fizzing) when a drop of diluted hydrochloric acid is applied. Common in the Midwestern USA, UK, and areas with exposed ancient sea beds.