Thaumasite in calcic skarns from the Zvezdel-Pcheloyad Pb-Zn deposit, Eastern Rhodopes, Bulgaria

Thaumasite was found in zoned calcic skarns hosted by the monzonitic rocks of the Zvezdel pluton, Eastern Rhodopes. Associated minerals are wollastonite, clinopyroxene, grossular-andradite garnets, Ti-rich garnets, plagio- clase, calcite, quartz, epidote, prehnite, and chlorite. Titanite, apatite and magnetite are present as accessories. The mineral has been characterized using optical microscopy, PXRD, SEM/EDS, EPMA, and FTIR. Thaumasite forms sheaf-like and fan-shaped aggregates, which consist of acicular crystals elongated along the c axis. The IR spectrum of thaumasite is in accordance with the chemical composition and contains absorption bands in the range 3500-3291 cm-1 (O-H stretching vibrations); 1683, 1650 cm-1 (bending vibrations of H2O); 1389 cm-1 (stretching vibrations of CO32-); 1100, 1069 cm-1 (asymmetric stretching vibrations of SO42-); 882 cm-1 (symmetric bending vibration of CO32-); 768, 742, 680 cm-1 (Si-O stretching vibrations of Si(OH)6 octahedra); 670 cm-1 (bending vibrations of SO42-).