gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1997.061.405.08 Mineralogy The Vibrational Spectra of BaMg(CO3)2 (Norsethite) Böttcher Michael E. Institute of Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University P.O. Box 2503, D-26111 Oldenburg, Germany Gehlken Peer-Lennart Testing of Raw and Residual Mineral Materials, Marktplatz 6-7, D-37308 Heiligenstadt, Germany Skogby Henrik Department of Mineralogy, Swedish Museum of Natural History, Box 50007, S-10405 Stockholm, Sweden Reutel Christian * 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

 4 1997 61 405 249 256 3 6 1996 31 7 1996 Copyright © 1997, The Mineralogical Society 1997 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