Mineralogical study of zeolites from Pentalofos area, Thrace, Greece

The zeolites of the Pentalofos area, Thrace, Greece, were studied by optical microscopy, X-ray diffraction (XRD) and Fourier Transform IR (FTIR) spectroscopy, in combination with thermoanalytical methods (thermogravimetric analysis (TG/DTG) and differential thermal analysis (DTA)). Their main mineral constituent (>90%) is “heulandite type-II”, an intermediate type of the isomorphous series heulandite–clinoptilolite end members. Feldspars, muscovite, biotite, quartz, and cristobalite were also detected. Traces of smectite were found in only few samples. The cation exchange capacity (CEC) of the Pentalofos zeolites (119 to 152 meq/100 g), as well as their low temperature dehydration behavior (during heating up to 350 °C, 15 of ∼22 molecules H2O are removed) are also characteristic for an intermediate member of the heulandite–clinoptilolite zeolite (“heulandite type-II”). These properties make them a powerful tool in the decontamination of waters and soils, in agriculture, in cement industry, etc. Moreover, this zeolite deposit is of a great economic interest, considering that it is the richest among the zeolite formations in Northeastern Greece (4.7×106 tons, with a zeolite content higher than 90%).