sedimentary

Sand Dollar Fossil (Echinoidea)

Class Echinoidea (likely order Clypeasteroida), CaCO3 (Calcite)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Off-white, grey, or earthen tan; Luster: Dull to chalky; Structure: Pentamerous (five-fold) symmetry with a petal-like pattern; Cleavage: None/Fragmentary.

Hardness: 3 on Mohs scale
Color: Off-white, grey, or earthen tan
Luster: Dull to chalky

Identified March 15, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Off-white, grey, or earthen tan; Luster: Dull to chalky; Structure: Pentamerous (five-fold) symmetry with a petal-like pattern; Cleavage: None/Fragmentary.

Formation & geological history

Formed through permineralization of the calcium carbonate exoskeleton (test) of an irregular sea urchin. These organisms lived in shallow marine environments. Geological age can range from the Eocene (56 million years ago) to the Holocene.

Uses & applications

Primarily used for educational purposes, fossil collecting, and occasionally in jewelry or decorative crafts due to their unique star pattern.

Geological facts

In folklore, they were sometimes called 'mermaid coins' or 'Sailor's coins'. Despite their flat appearance, they are biological relatives of sea urchins and starfish. Many specimens found on beaches are modern, but 'heavy', stone-like versions are true fossils found in sedimentary rock layers.

Field identification & locations

Identify by looking for the 'petaloid' pattern (the five-pointed star) and the flat, disc-like shape. In the field, look for them in limestone or sandstone outcrops near coastal regions or ancient seabeds.