BACTERIAL ORIGIN OF THE RED PIGMENTATION IN THE DEVONIAN SLIVENEC LIMESTONE, CZECH-REPUBLIC

The deep-red lenses of the Pragian Slivenec Limestone have been extens ively quarried for ornamental purposes since the XIIth century. Petrog raphic microscope observations indicate that the hematite stainings of the limestone follow ten different patterns. They range from massive non-directional filling of cavities to mineralized films and microstro matolites. Numerous iron-rich endolithes are observed. Some could be d erived from bacterial or lichen perforations and some related to ferri c bacteria. Infiltration along welded calcite crystals, regular minera lized films and microstromatolites suggest a ferric bacterial origin f or the pigment. This is confirmed by scanning microscope examinations of polished sections, that show hematite concentrations along micromet ric filamentous sheaths.