sedimentary
Crinoid Fossil Marble
Crinoidal Limestone / Phylum Echinodermata
Hardness: 3-4 (Mohs scale); Color: Dark grey or black matrix with white or cream fossils; Luster: Dull to earthy; Structure: Biogenic fragments in a fine-grained matrix; Cleavage: None (conchoidal fracture in matrix).
- Hardness
- 3-4 (Mohs scale)
- Color
- Dark grey or black matrix with white or cream fossils
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: Dark grey or black matrix with white or cream fossils; Luster: Dull to earthy; Structure: Biogenic fragments in a fine-grained matrix; Cleavage: None (conchoidal fracture in matrix).
Formation & geological history
Formed through the accumulation of skeletal remains from crinoids (sea lilies) on the ocean floor during the Paleozoic era (approx. 300-500 million years ago), which were then lithified into limestone.
Uses & applications
Primarily used for educational collecting, decorative stone, lapidary work (polishing into pebbles), and occasionally in architectural tiling or fireplace surrounds.
Geological facts
Crinoids are actually animals (echinoderms) related to starfish and sea urchins, not plants, despite their 'sea lily' nickname. The circular patterns in this specimen are cross-sections of the animal's stem.
Field identification & locations
Identifiable by the distinct 'cheerio' or star-shaped white circles embedded in a darker rock. Commonly found in limestone-rich regions like the UK (Derbyshire), the Midwestern US, and Morocco.
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