KLEINITE FROM TERLINGUA, BREWSTER-COUNTY, TEXAS - INVESTIGATIONS BY SINGLE-CRYSTAL X-RAY-DIFFRACTION, AND VIBRATIONAL SPECTROSCOPY

Modern single crystal X-ray work on kleinite [a = 6.762(2), c = 11.068 (3)Angstrom; space group: P6(3)/mmc; Z = 4] confirmed the high-tridymi te type Hg2N+ framework. Anions, and anion groups like Cl-, and SO42- or H2O molecules are located within large open channels running parall el to [001]. These groups are statistically and/or dynamically disorde red. Reversible order-disorder phenomena of these groups within the Hg 2N+ framework are responsible for the change of the whole symmetry fro m ''hexagonal'' to monoclinic or even triclinic and vice versa. Vibrat ional spectroscopy shows clearly the presence of disordered SO4 groups , and low H2O content in the above mentioned channels.