Michał Sachanbiński and Adam Szuszkiewicz
Alexej N. Platonov and Adam Szuszkiewicz
The green colour of prasiolite, defined as naturally occurring transparent macrocrystalline α-quartz with primary colouration, results from the optical absorption centred at ~13,660 cm−1 and attributed to the FeVI 2+→FeVI 3+ intervalence charge transfer (Platonov et al. 1992). However, optical absorption spectroscopy of blue-green to green quartz from Rakowice Wielkie, Sudetes, south-western Poland, shows that its primary colouration results from the combination of this band and absorptions at ~18,500 cm−1 and ~16,250 cm−1. The first is assigned to a hole centre Fe4+ s(Fe3+ s-e−) combined with an electron centre Fe2+ I6(Fe3+ I6+e−), while the second from AlO4 4− defects. The quartz is blue-green if the 18,500 cm−1 prevails and becomes pale green if the 16,250 cm−1 band predominates. These colours seem to represent intermediate colour varieties between amethyst and prasiolite. We also suggest that spectral features of coloured quartz varieties might be useful indicators of changes in the physical- and chemical characteristics of the mineral-forming fluids.
Antoni Muszer, Adam Szuszkiewicz and Krzysztof Łobos
New Occurrence of Clausthalite (PbSe) in the Sudetes (SW Poland)
The presence of clausthalite in the area of old mining works near Dziećmorowice in the Sowie Mts (SW Poland) is reported here for the first time. The identification of the clausthalite is based on macro- and microscopic observations, reflectance measurements, chemical analyses and X-ray diffraction data. The clausthalite, together with uraninite, forms veinlets in a breccia comprising <50% calc-silicate rock fragments. Different polishing hardnesses suggest some variation in the mineral structure of individual clausthalite grains. Chemical spot analyses do not reveal elements other than Pb and Se though calculated unit-cell parameters may suggest minor substitution of S for Se.