The crystal structure of a biogenic aragonite from the nacre of an ammonite shell

Journal Article · Tue Feb 07 04:00:00 EST 2012 · RSC Advances

DOI:https://doi.org/10.1039/C1RA00568E· OSTI ID:1033013

Antao, S M ^[1]

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1. Calgary

The crystal structure of a biogenic aragonite from the nacre of an ammonite shell was obtained using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinement. The well-preserved ammonite sample is from Alberta, Canada, and is from the Cretaceous period. The aragonite structure was refined in space group Pmcn, Z = 4, and the cell parameters obtained are a = 4.96265(2), b = 7.97016(4), c = 5.74474(3) {angstrom}, and V = 227.222(2) {angstrom}{sup 3}. The chemical analyses indicate a formula of [Ca{sub 0.995}Sr{sub 0.004}Ba{sub 0.001}]{Sigma} = 1.0(CO{sub 3}). The average <Ca-O> and <C-O> distances are 2.5281(3) and 1.2871(6) {angstrom}, respectively, and the average <O-C-O> angle is 119.94(8){sup o}. The CO{sub 3} groups are non-planar. Based on crystal-structure data for biogenic and non-biogenic aragonite samples, aragonite from ammonite nacre has minimal structural distortions and is very similar to non-biogenic aragonite, in particular, a sample from Spain.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: FOREIGN
• OSTI ID: 1033013
• Journal Information: RSC Advances, Journal Name: RSC Advances Journal Issue: 2 Vol. 2
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

58 GEOSCIENCES
ARAGONITE
CRETACEOUS PERIOD
CRYSTAL STRUCTURE
SPACE GROUPS
SYNCHROTRONS
X-RAY DIFFRACTION