sedimentary
Echinoid Fossil (Sea Urchin)
Echinoidea (specifically likely Schizaster or similar genus), calcium carbonate (CaCO3)
Hardness: 3 (calcite preservation). Color: Tan, brown, or gray. Luster: Dull/earthy. Crystal structure: Trigonal (as calcite replacement). Features: Distinct five-fold radial symmetry (pentamerism) often visible as star-shaped patterns on the top.
- Hardness
- 3 (calcite preservation)
- Color
- Tan, brown, or gray
- Luster
- Dull/earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3 (calcite preservation). Color: Tan, brown, or gray. Luster: Dull/earthy. Crystal structure: Trigonal (as calcite replacement). Features: Distinct five-fold radial symmetry (pentamerism) often visible as star-shaped patterns on the top.
Formation & geological history
Formed in marine environments through the mineralization of sea urchin exoskeletons. These typically range from the Ordovician period to the present, with many common specimens dating to the Cretaceous or Paleogene (approx. 66–23 million years ago).
Uses & applications
Primarily used for educational purposes, scientific study, and as decorative items for fossil collectors. In some cultures, they have been used as amulets or 'thunderstones'.
Geological facts
Commonly known as 'shepherd's crowns' or 'fairy loaves' in English folklore, they were historically believed to protect against witchcraft or ensure bread always rose in the oven.
Field identification & locations
Identify in the field by looking for disc-like or heart-shaped stones with a clear star pattern on one side and a rough, pitted texture. Commonly found in limestone quarries, chalk deposits, or coastal cliffs (e.g., Texas, UK, France).
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary