fossil

Fossil Sea Urchin / Echinoid

Class Echinoidea

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale (due to calcite composition); Color: Typically white, cream, tan, or gray; Luster: Dull to vitreous; Crystal structure: Trigonal (calcite); Specific gravity: 2.71

Hardness: 3 on Mohs scale (due to calcite composition)
Color: Typically white, cream, tan, or gray
Luster: Dull to vitreous

Identified July 31, 2026More fossil →

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Physical properties

Hardness: 3 on Mohs scale (due to calcite composition); Color: Typically white, cream, tan, or gray; Luster: Dull to vitreous; Crystal structure: Trigonal (calcite); Specific gravity: 2.71

Formation & geological history

Formed through the process of permineralization or fossilization, where the hard calcium carbonate test (shell) of a marine echinoid is preserved in sedimentary layers, often dating from the Paleozoic to Cenozoic eras.

Uses & applications

Used in educational exhibits, fossil collecting, and decorative display items.

Geological facts

Commonly known as 'fairy loafs' or 'shepherd's crowns' in European folklore, fossilized sea urchins were historically placed on windowsills to protect homes from lightning.

Field identification & locations

Found in marine sedimentary rocks like limestone and chalk formations worldwide. Collectors look for the distinctive five-petal star pattern (ambulacral grooves) on the upper surface.