sedimentary
Fossiliferous Limestone (Crinoidal)
Calcium Carbonate (CaCO3) - Limestone containing bioclasts
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 More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
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
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.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary