Phys Chem Minerals (2007) 34:551–558 DOI 10.1007/s00269-007-0170-x 123 ORIGINAL PAPER A Raman spectroscopic investigation of Fe-rich sphalerite: eVect of fe-substitution Sherif Kharbish Received: 8 January 2007 / Accepted: 1 June 2007 / Published online: 12 July 2007  Springer-Verlag 2007 Abstract A Raman spectroscopic study of Fe-rich sphal- erite (Zn 1 ¡ x Fe x S) has been carried out for six samples with 0.10 · x · 0.24. Both the intensities and frequencies of the TO and LO modes of sphalerite are approximately indepen- dent of Fe concentration. However, the substitution of Zn by Fe results in Wve additional bands with frequencies between the TO (271 cm ¡1 ) and LO (350 cm ¡1 ) modes. Three of these bands are attributed to resonance modes (i.e. Y 1 , Y 2 and Y 3 modes). The fourth band (B mode) is assigned to a breath- ing mode of the nearest-neighbor sulfur atoms around the Fe atoms. The band at 337 cm ¡1 is attributed to the presence of Fe 3+ . The excellent correlations between the normalized intensities of these Wve diVerent modes and x Fe show that these modes depend on Fe-content. Another extra mode at 287 cm ¡1 is assigned to the presence of Cd in sphalerite. Keywords Fe-rich sphalerite · Cd-sphalerite · Resonance modes · Breathing mode · Raman spectroscopy Introduction The mineral sphalerite (ZnS) is the major ore of zinc. It crystallizes in space group F-43 m. The structure of sphal- erite is closely related to the structure of diamond and the zinc and sulfur atoms are tetrahedrally coordinated. Sphal- erite consists largely of zinc sulWde but almost always con- tains variable amounts of Fe, Cd and Mn. The lattice parameter of sphalerite can be expressed in terms of its composition by the function a (Å) = 5.4093 + 0.000456X + 0.00424Y + 0.00202Z, where X, Y and Z are the contents of FeS, CdS and MnS in mol %, respectively (Skinner 1961). Literature data for structural parameters (Barton and Toulmin 1966), Mössbauer and infrared (IR) spectroscopy (Keys et al. 1968; Gerard et al. 1971; Scott 1971) and den- sity determinations (Cabri 1969) diVer drastically with regard to the occurrence of Fe 3+ in sphalerite. Manning (1967) mentioned that the optical absorption spectra of Fe- containing sphalerite suggested the presence of Fe 2+ in the tetrahedral substitutional sites and Fe 3+ in the octahedral interstitial sites. Gerard et al. (1971) detected by Mössbauer spectroscopy small amounts of Fe 3+ in Fe-rich sphalerite. In addition, Lepetit et al. (2003) mentioned that up to 10 mol % FeS, the lattice parameter of sphalerite increases with the increase of FeS, whereas above about 10 mol % the lattice parameter strongly depends on the Fe 3+ /Fe 2+ ratio, con- trolled by S fugacity. Primary Raman investigations showed that sphalerite has two optic phonons, i.e., longitudinal-optic (LO) and transverse-optic (TO) modes, both of which are Raman active (Schneider and Kirby 1972). The Wrst-order Raman spectra of sphalerite revealed the LO and TO modes at 349 and 274 cm ¡1 (Couture-Mathieu and Mathieu 1953) or at 352 and 271 cm ¡1 (Nilsen 1969), respectively. The second- order Raman spectra showed additional modes, e.g., TA and LA at 88 and 110 cm ¡1 , respectively (Nilsen 1969). Raman scattering studies of the eVects of substituting relatively small amounts (»1%) of Fe, Mn, Co or Cr for Zn revealed new modes. The frequencies of all new modes were found between the LO and TO modes (Zigone et al. 1981). The frequencies of those modes were approximately S. Kharbish (&) Institut für Mineralogie und Kristallographie, Universität Wien-Geozentrum, Althanstraße 14, 1090 Wien, Austria e-mail: sherifkharbish@hotmail.com S. Kharbish Geology Department, Faculty of Science, Zagazig University, Zagazig City, El-Sharkia Egypt