The Vibrational Spectra of BaMg(CO3)2 (Norsethite)

Michael E. Böttcher, Peer-Lennart Gehlken, Henrik Skogby and Christian Reutel*
Institute of Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University P.O. Box 2503, D-26111 Oldenburg, Germany
Testing of Raw and Residual Mineral Materials, Marktplatz 6-7, D-37308 Heiligenstadt, Germany
Department of Mineralogy, Swedish Museum of Natural History, Box 50007, S-10405 Stockholm, Sweden
Institute of Geology and Dynamics of the Lithosphere (IGDL), Georg-August-University, Goldschmidtstr.3, D-37077 Göttingen, Germany
*Present address: GeoLink, Düstere-Eichenweg 1, D-37073 Göttingen, Germany

Abstract: The FTIR spectra of synthetic BaMg(CO3)2 (norsethite) are measured at ambient temperature and atmospheric pressure, and the influence of formation conditions on the FTIR spectra is investigated. The results are compared with those for natural norsethite from Långban (Sweden) and Rosh Pinah (Namibia). The Raman spectrum of synthetic norsethite is reported, too. A number of first-order internal modes of the carbonate ion group (ν1, ν2, ν3, ν4) are found to be infrared and Raman active. Additonally, the (ν1+ν3) and (ν1+ν4) combination modes and the (2*ν2) overtone are observed in the FTIR and Raman spectrum, respectively. The carbon isotopic-shift coefficient for ν2 due to the substitution of 12C by C13(ν2(CO32−13)∕ν2(CO32−12)=0.971±0.002), observed by FTIR spectroscopy, agrees with the theoretical value of 0.969.

Keywords: norsethite • BaMg(CO3)2 • synthesis • formation conditions • phase diagram • carbon isotopes • Fourier transform infrared spectroscopy • Raman spectroscopy

Mineralogical Magazine; April 1997 v. 61; no. 405; p. 249-256; DOI: 10.1180/minmag.1997.061.405.08
© 1997, The Mineralogical Society
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