Characterization and identification of carbonate and sulfide minerals from the Republic Macedonia by infrared and Raman Spectroscopy

Some of the sulfide minerals appear as well-formed crystal species in the nature, but often their appearance is accompanied with other minerals. Thus, the difficulties connected with the separation, identification and characterization of several sulfide minerals: galena, Pb S; sphalerite Zn S; pyrite, FeS2; chalcopyrite, CuFeS2; realgar, AS4S4; orpiment, As2S3 and stibnite, Sb2S3 collected from various localities from the Republic of Macedonia (Sasa, Buchim, Zletovo, Alshar) are discussed. The study of these minerals was performed using Fourier- transform infrared (FT IR) and Raman vibrational spectroscopy in order to assign the bands in the corresponding spectra as well as to compare the results with the corresponding literature data for the analogous mineral species originating all over the world. The infrared and Raman spectra of group of four sulfo salts, including lorandite (TIAsS2) and three other MIMIIIS2 type synthetic minerals (smithite, AgAsS2: weissbergite, TISbS2 and miargyrite, AgSbS2) are studied at room temperature. Their vibrational spectra are compared with the corresponding spectra of MIII2S3 type minerals: orpiment, As2S3 and stibnite, Sb2S3. In spite of different crystal structures of these minerals, a similarity between the vibrational spectra of the arsenic minerals, on the one hand, and the antimony minerals, on the other hand, has been detected. The spectra are discussed in terms of their structural similarities and differences between the minerals containing As atom, and those which contain Sb atoms. An additional group of four MI3MIlIS3 type synthetic minerals (proustite. Ag3AsS3; ellisite, Tl3AsS3; pyrargyrite, Ag3SbS3; stibioellisite, Tl3SbS3) are also studied by FT IR and micro-Raman spectroscopy. In general, rather expressed similarity between the corresponding spectra of the MI3AsS3 minerals and particularly between the MI3SbS3 minerals (MI = Ag or Tl) is observed. The similar spectral behavior is attributed to the presence of the MIlIS3 pyramids (MlII As or Sb) as main structural and vibrational units in the minerals. The carbonate group of several minerals from the calcite group (calcite. CaCO3. magnesite, MgCO3; siderite, FeCO3) as well as the dolomite group [dolomite, CaMg(CO3)2; kutnahorite, CaMn(CO3)2] found in Macedonia (Alshar, Zletovo, Sasa, Damjan. Mrzen, Sivec, Trojaci, Pchinja) are also studied using FT IR spectroscopy. The observed frequency difference between the corresponding ν3, ν2and ν4 modes (of CO3 groups) in their spectra is used to discriminate between these carbonate minerals from one another as well as to determine the presence of impurities of some on them in the corresponding two-component carbonate mixtures. (Author)