Chromatite Ca[CrO4] in soil polluted with electroplating effluents (Zabierzów, Poland)

Chromatite, Ca[CrO4] (space group I41/amd), was found as yellow precipitates between the particles of soil, heavily polluted with chromium(VI)-bearing electroplating effluents and weathered subsoil rocks (marly limestones, marls). X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM) have showed the precipitates to be almost pure Ca[CrO4]. The chromatite occurs mainly as coatings 5-30 μm large and prismatic grains 20-100 μm long. It was formed and preserved due to dissolution of calcium carbonate by electroplating effluents containing Cr(VI). Although precipitation of calcium chromates in the soils polluted with chromium(VI) compounds has already been mentioned in the literature, the author gives the first mineralogical description of the chromatite formed in such an environment.