Rock · Concretion
Septarian
CaCO3 (calcite) with aragonite and clay
Septarian nodules are carbonate concretions with shrinkage cracks filled by yellow calcite and brown aragonite, cut and polished from the Cretaceous of Utah (Orderville), Madagascar (Mahajanga) and the Jurassic of England. Madagascan septarians sometimes contain ammonites or belemnites and are sold as spheres and hearts. They are rocks, not mineral species, and are cheap and decorative.
| Formula | CaCO3 (calcite) with aragonite and clay |
|---|---|
| IMA status | rock |
| Mohs hardness | 3–4 |
| Group | Concretion |
| Type locality | None |
Elsewhere
- Wikidata: Q583793
- Mindat: Septarian
- Wikipedia: Septarian
Cite this article
Stratum Study. "Septarian" (Mineral). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/minerals/septarian. Accessed 2026-09-20.
@misc{stratum-septarian,
title = {Septarian},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/minerals/septarian}},
year = {2026},
note = {Mineral article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, wikidata, commons. Accessed 2026-09-20.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.