Mineral · Aragonite group
Aragonite
CaCO3
Aragonite is the orthorhombic form of calcium carbonate, found as pseudohexagonal twins from Spain and Morocco, the spiky 'sputnik' clusters of Sicily and Spain, coral-like flos ferri from Austria and as the shell material of molluscs and ammonites. It is metastable and converts to calcite over geological time, which is why most fossil shell is calcite. Morocco exports orange sputnik aragonite by the pallet.
| Formula | CaCO3 |
|---|---|
| IMA status | grandfathered |
| Crystal system | Orthorhombic |
| Mohs hardness | 3.5–4 |
| Group | Aragonite group |
| Type locality | Molina de Aragón, Guadalajara, Spain |
| Streak | White |
| Specific gravity | 2.94 |
| Reference list | IMA List of Minerals (RRUFF) — verify formula and status against the current list |
Fakes and treatments
Moroccan aragonite is sometimes dyed or artificially iron-stained; 'coral aragonite' names are marketing.
Elsewhere
Cite this article
Stratum Study. "Aragonite" (Mineral). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/minerals/aragonite. Accessed 2026-09-20.
@misc{stratum-aragonite,
title = {Aragonite},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/minerals/aragonite}},
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.