THE VIBRATIONAL-SPECTRA OF BAMG(CO3)(2) (NORSETHITE)

The FTIR spectra of synthetic BaMg(CO3)(2) (norsethite) are measured a t ambient temperature and atmospheric pressure, and the influence of f ormation conditions on the FTIR spectra is investigated. The results a re compared with those for natural norsethite from Langban (Sweden) an d Rosh Pinah (Namibia). The Raman spectrum of synthetic norsethite is reported, too. A number of first-order internal modes of the carbonate ion group (nu 1, nu 2, nu 3, nu 4) are found to be infrared and Raman active. Additonally, the (nu 1+nu 3) and (nu 1+nu 4) combination mode s and the (2nu 2) overtone are observed in the FTIR and Raman spectru m, respectively. The carbon isotopic-shift coefficient for nu 2 due to the substitution of C-12 by C-13 (nu 2((CO32-)-C-13)/nu 2((CO32-)-C-1 2) = 0.971 +/- 0.002), observed by FTIR spectroscopy, agrees with the theoretical value of 0.969.