engleski

Minerals from Macedonia. Discrimination among Calcite and Aragonite by powder X-ray diffraction and FT IR spectroscopy

The most frequently used techniques for mineral detection, identification, discrimination as well as their quantitative determination developed during the last few decades are X-ray diffraction, thermal analysis, optical diffuse reflectance, Raman and infrared vibrational spectroscopy. Since all these techniques have their own advantages and imperfections, in general, it is strongly recommendable (especially in the case of mineral characterization) to use them complementary rather than competitive. Often, however, it is advantageous to use or to develop simple and rapid methods for mineral discrimination as well as for detection of their impurities in mineral mixtures using only one of the above mentioned techniques. X-ray powder diffraction and FT infrared spectroscopy fulfill the above requirements providing the results quickly and giving a very rapid indication about the presence of the existing impurities. In that sense, as a part of a broader study of the structural and spectroscopic characteristics of the minerals originating from Macedonia, we studied the analytical application of the FT IR spectra as well as X-ray diffraction patterns of some carbonate minerals. Here we present comparatively the use of the powder X-ray diffraction and FT IR spectroscopy to distinguish among the geologically important carbonate minerals calcite and aragonite as well as to detect and determine mineral impurities in their mixtures. It was shown that the limit of detection of calcite in aragonite and vice versa using the FT IR spectroscopy is around 2 % impurities, whereas the presence of even lower than 0.5 % impurities of calcite in aragonite can be detected by powder X-ray diffraction.

Calcite; Aragonite; X-ray powder diffraction; FT IR spectroscopy

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