Tugtupite Antao S M, Hassan I, Parise J B American Mineralogist 89 (2004) 492-497 Tugtupite: High-temperature structures obtained from in situ synchrotron diffraction and Rietveld refinements T = 20 C, data from Hassan and Grundy (1991) _database_code_amcsd 0003450 8.640 8.640 8.873 90 90 90 I-4 atom x y z Uiso Al 0 .5 .75 .0075 Be 0 .5 .25 .0098 Si .0127 .2533 .4958 .0075 O1 .1504 .1343 .4417 .0121 O2 .3472 .0385 .6488 .0121 O3 .4256 .1486 .1377 .0121 Na .1563 .1972 .1818 .0188 Cl 0 0 0 .0234