... NaNa 2 Mg 5 Si 8 O 21 (OH) 3 ( Cámara et al. 2004 ). Two end-member compositions were prepared as silicate gels, following the method of Hamilton and Henderson (1968) ; intermediate compositions were obtained by mixing the gels in stoichiometric amounts (Table 1 ). Hydrothermal synthesis...

... 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...

... to the discovery of: (1) sadanagaite, calcic amphiboles of ideal compositions A R + B Ca 2 C (R 2+ 3 R 3+ 2 ) T (Si 5 Al 3 ) O 22 W (OH) 2 ( Shimazaki et al. 1984 ; Sokolova et al. 2000 ; Banno et al. 2004 ; Nishio-Hamane et al. in prep.); (2) fluorocannilloite, a calcic amphibole of ideal composition...

... [=Na 2 Mg 8 Si 12 O 30 (OH) 6 ], and JT [=Mg 10 Si 12 O 32 (OH) 4 ]. The dotted rectangle is the area defined by the 1σ uncertainties in the electron microprobe analyses of the Na-cjt phase studied here. The black triangle shows the field of Na-Mg-rich amphiboles bounded by the ideal compositions 3:5...

... 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 and Della Ventura 2007 , this volume). Infrared...

... Chem Soc 102 : 4889 – 4893 Liu SX , Welch , MD , Klinowski J , Maresch , WV ( 1996 ) A MAS NMR study 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...