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, plagioclase, 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–).