Natrolitite, an unusual rock - Occurrence and petrographic and geochemical characteristics (Eastern Turkey) - Çiftçi, Emín (Nigde University. Department of Geological Engineering) ; Hogan, John P. (University of Missouri-Rolla. Department of Geology and Geophysics) ; Kolayli, Hasan (Karadeniz Technical University. Department of Geological Engineering) ; Çadirli, Emín (Nigde University. Department of Physics)