A nanocrystalline monoclinic CaCO3 precursor of metastable aragonite

Péter Németh, Enrico Mugnaioli, Mauro Gemmi, György Czuppon, A. Demény, Christoph Spötl

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Despite its thermodynamical metastability at near-surface conditions, aragonite is widespread in marine and terrestrial sediments. It abundantly forms in living organisms, and its abiotic formation is favored in waters of a Mg2+/Ca2+ ratio > 1.5. Here, we provide crystallographic evidence of a nanocrystalline CaCO3 polymorph, which precipitates before aragonite in a cave. The new phase, which we term monoclinic aragonite (mAra), is crystallographically related to ordinary, orthorhombic aragonite. Electron diffraction tomography combined with structure determination demonstrates that mAra has a layered aragonite structure, in which some carbonates can be replaced by hydroxyls and up to 10 atomic % of Mg can be incorporated. The diagnostic electron diffraction features of mAra are diffuse scattering and satellite reflections along aragonite {110}. Similar features have previously been reported—although unrecognized—from biogenic aragonite formed in stromatolites, mollusks, and cyanobacteria as well as from synthetic material. We propose that mAra is a widespread crystalline CaCO3 that plays a hitherto unrecognized key role in metastable aragonite formation.

Original languageEnglish
Article numbereaau6178
JournalScience advances
Volume4
Issue number12
DOIs
Publication statusPublished - Dec 12 2018

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Calcium Carbonate
Electron Microscope Tomography
Geologic Sediments
Mollusca
Carbonates
Cyanobacteria
Hydroxyl Radical
Electrons

ASJC Scopus subject areas

  • General

Cite this

Németh, P., Mugnaioli, E., Gemmi, M., Czuppon, G., Demény, A., & Spötl, C. (2018). A nanocrystalline monoclinic CaCO3 precursor of metastable aragonite. Science advances, 4(12), [eaau6178]. https://doi.org/10.1126/sciadv.aau6178

A nanocrystalline monoclinic CaCO3 precursor of metastable aragonite. / Németh, Péter; Mugnaioli, Enrico; Gemmi, Mauro; Czuppon, György; Demény, A.; Spötl, Christoph.

In: Science advances, Vol. 4, No. 12, eaau6178, 12.12.2018.

Research output: Contribution to journalArticle

Németh, P, Mugnaioli, E, Gemmi, M, Czuppon, G, Demény, A & Spötl, C 2018, 'A nanocrystalline monoclinic CaCO3 precursor of metastable aragonite', Science advances, vol. 4, no. 12, eaau6178. https://doi.org/10.1126/sciadv.aau6178
Németh, Péter ; Mugnaioli, Enrico ; Gemmi, Mauro ; Czuppon, György ; Demény, A. ; Spötl, Christoph. / A nanocrystalline monoclinic CaCO3 precursor of metastable aragonite. In: Science advances. 2018 ; Vol. 4, No. 12.
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