sedimentary
Fossiliferous Limestone with Crinoid stems
Calcite-rich Biogenic Sedimentary Rock (CaCO3)
Hardness: 3 on Mohs scale; Color: light grey to off-white; Luster: dull/earthy; Structure: clastic/biogenic with visible circular fossil impressions; Cleavage: none (fractures across fossils).
- Hardness
- 3 on Mohs scale
- Color
- light grey to off-white
- Luster
- dull/earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: light grey to off-white; Luster: dull/earthy; Structure: clastic/biogenic with visible circular fossil impressions; Cleavage: none (fractures across fossils).
Formation & geological history
Formed in a shallow marine environment from the accumulation of skeletal remains like crinoids, shells, and coral. This particular specimen likely dates to the Paleozoic era (approx. 250-500 million years ago).
Uses & applications
Primarily used in construction (crushed stone, cement), agriculture (lime), and as educational fossil specimens for collectors and students.
Geological facts
Crinoids are also known as 'sea lilies' even though they are animals related to starfish. The small circular 'Cheerio' like holes or rings on this specimen represent the individual segments of the crinoid's stem.
Field identification & locations
Identify by looking for small disc-shaped or star-shaped impressions or holes in a soft, light-colored rock that fizzes when exposed to vinegar (weak acid). Commonly found in areas with historic seafloors like the Midwest USA and Great Lakes region.
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