... be incorporated in the amphibole, and the structure changes to the unusual C 1̅ space group, with the ideal composition NaNa 2 Mg 5 Si 8 O 21 (OH) 3 ( Cámara et al. 2004 ). Oberti et al. (2000) studied recently a synthetic crystal obtained by Maresch and Langer (1976) in the Li-bearing LNMSH system...

... diffraction data. Experimental work in the Na 2 O-MgO-SiO 2 -H 2 O system also showed the existence of a stable amphibole composition with three protons per formula unit, i.e., NaNa 2 Mg 5 Si 8 O 21 (OH) 3 , which is related to Na(NaMg)Mg 5 Si 8 O 22 (OH) 2 by the Na1H1Mg–1 exchange. The former amphibole...

...Fernando Cámara; Roberta Oberti; Giancarlo Della Ventura; Mark D. Welch; Walter V. Maresch Abstract Synthetic NaNa 2 Mg 5 Si 8 O 21 (OH) 3 is the first triclinic member of the amphibole group, and has a tripling of the unit cell in the b direction. The space group is C 1̅ and the triple- b repeat...

... Pnmn 1986-007 1,2*     clino-sodic-ferri-ferroholmquistite A □ B Li 2 C (Fe 2+ 3 Fe 3+ 2 ) T Si 8 O 22 W (OH) 2 C 2/ m 1995-045b 3     sodic-ferripedrizite A Na B Li 2 C (Mg 2 Fe 3+ 2 Li) T Si 8 O 22 W (OH) 2 C 2/ m 1998-061 4     proto-anthophyllite A □ B...

... studied here. The black triangle shows the field of Na-Mg-rich amphiboles bounded by the ideal compositions 3:5 [=Na 3 Mg 5 Si 8 O 21 (OH) 3 ], 2:6 [=Na 2 Mg 6 Si 8 O 22 (OH) 2 ], and 2:5 [=Na 2 Mg 5 Si 8 O 20 (OH) 4 ]. The black rectangle is the area defined by the uncertainties in the microprobe...

... minerals. Infrared spectroscopy has proven a very effective probe for determining short-range cation and anion order in amphiboles, due to the high sensitivity of the OH-stretching frequency to the occupancies of the adjacent M (1) and M (3) sites, and to more distant interactions (see Hawthorne...

... of a monoclinic/triclinic phase transition in an amphibole with excess OH - Na 3 Mg 5 Si 8 O 21 (OH)3 . Eur J Mineral 8 : 223 – 229 Liu , SX ; Welch , MD ; Klinowski , J ( 1997 ) NMR study of phase transitions in guest-free silica clathrate melanophlogite . J Phys Chem B 101 : 2811...