sedimentary (fossil)

Fossilized Sea Urchin (Echinoid)

Echinoidea (Class); commonly Clypeasteroida for sand dollar types

Hardness: 3 (calcified); Color: tan, grey, or off-white; Luster: matte/earthy; Crystal Structure: Trigonal (calcite replacement); Key feature: five-fold radial symmetry (pentamerism) with petal-like patterns.

Hardness: 3 (calcified)
Color: tan, grey, or off-white
Luster: matte/earthy

Identified March 23, 2026More sedimentary (fossil) →

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Physical properties

Formation & geological history

Formed through the permineralization of marine echinoderm exoskeletons in shallow marine environments. Most common specimens range from the Cretaceous to the Neogene periods (approx. 145 to 2.5 million years ago).

Uses & applications

Primarily used for educational purposes, scientific study (paleontology), and architectural/home decor; often used as introductory pieces for mineral and fossil collectors.

Geological facts

In folklore, these fossils were often called 'fairy loaves' or 'thunderstones.' They are more closely related to modern sea stars and sea cucumbers than they are to fish or other sea life.

Field identification & locations

Identify by looking for the distinct 'petal' pattern on a rounded, dome-shaped, or flattened calcified body. Commonly found in limestone quarries, chalk cliffs, or coastal sedimentary outcrops in Europe, Northern Africa, and the USA (notably Texas and Florida).

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