Fossils in thin section

Echinoderms (crinoids, echinoids) in thin section

Plates, spines and ossicles of magnesian calcite. Each plate or spine goes extinct as a single crystal under crossed polars. Crinoid plates show a reticulate (mesh) pattern and often look dusty where pores filled with micrite or inclusion-rich cement. Crinoid columnals are donut-shaped segments with a central canal, sometimes with five-fold symmetry. Crinoid fragments often form ooid cores.

**Crinoid columnals cut in different orientations.** Michael C. Rygel via Wikimedia Commons, CC BY-SA 4.0. Source

**Crinoid elements: stacked columnals, arm plate, five-fold symmetry, ooid cores.** Michael C. Rygel via Wikimedia Commons, CC BY-SA 4.0. Source

Photos are hosted by their original sites and shown under their open licenses (CC BY, CC BY-SA, public domain or Open Government Licence). Click a photo for its source page.

More photomicrographs

Alex Strekeisen: Syntaxial overgrowth · Alex Strekeisen: Encrinite

All fossil groups Carbonate classification

Sources

SEPM Strata: Skeletal Grains · Rygel & Quinton, Sedimentary Geology 9.7: Fossils in Thin Section