sedimentary
Crinoid Fossil in Limestone
Crinoidea fossil (stalk segments) in Calcium Carbonate (CaCO3) matrix
Hardness: 3 (limestone matrix); Color: Tan, beige, or grey with white fossil inclusions; Luster: Dull/earthy; Crystal Structure: Rhombohedral (calcite crystals in fossil); Cleavage: Perfect in calcite segments.
- Hardness
- 3 (limestone matrix)
- Color
- Tan, beige, or grey with white fossil inclusions
- Luster
- Dull/earthy
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Physical properties
Hardness: 3 (limestone matrix); Color: Tan, beige, or grey with white fossil inclusions; Luster: Dull/earthy; Crystal Structure: Rhombohedral (calcite crystals in fossil); Cleavage: Perfect in calcite segments.
Formation & geological history
Formed in warm, shallow marine environments during the Paleozoic era (approx. 250-500 million years ago) through the accumulation of skeletal remains and lime mud.
Uses & applications
Educational specimens, fossil collecting, and limestone is used in cement production and construction.
Geological facts
Crinoids are often called 'sea lilies' but are actually animals related to starfish and sea urchins. The disk-like segments of the stem are known as columnals.
Field identification & locations
Identify in the field by looking for 'Cheerio' shaped rings or ribbed cylindrical indentations in sedimentary stone. Common in the American Midwest and limestone quarries worldwide.
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