Micro-Raman spectra of extremely rare and endemic Tl-sulfosalts from Allchar deposit

摘要

The micro-Raman spectra of the extremely rare Tl-sulfosalts from Allchar (fangite, vrbaite, raguinite and rebulite) are presented and the bands are assigned for the first time although the minerals are known at least for 30 years. For the ease of the interpretation, the spectra-structure correlations were derived with the assistance of other natural Tl-containing minerals also collected from Allchar (lorandite and parapierrotite) and other synthetic Tl-analogues (ellisite, stibioellisite, and weissbergite), whose spectral characteristics have already been described. The similarities occurring in the Raman spectra arise from the presence of XS_3 trigonal pyramids (X = As and/or Sb) and/or XS_4 tetrahedral units (X = As and Fe) in the structure of all discussed Tl-sulfosalts. In addition, particular attention is stressed on the used laser intensity, establishing proper individualized protocol for each laser-sensitive Tl-sulfosalt.