Disordered Natrolite of Neuquen, Patagonia Argentina

VATTUONE, M.E.; CROSTA, S.; BERBEGLIA, Y.; LATORRE, C.O.; MARTÍNEZ DOPICO, C.I.; GALLEGOS, E.

Santa Fé, New Mexico

Encuentro; 44th Annual Meeting of the Clay Minerals Society; 2007

Clay Minerals Society

Natrolite has been found in an alkaline zeolite assemblage in an amygdaloid basalt in Junín de los Andes, Neuquén province, Argentina, as noted Vattuone et al. (2005). Following Gaines et al. (1997) and Deer, et al. (2004), the degree of ordering in the structure of natrolite is estimated using the difference between the b and a unit cell dimensions. In ?fully ordered? natrolite b-a = 0.35 Å, and in the disordered type, ?Na-rich gonnardite (ex tetranatrolite)? b-a = 0 Å (completely disordered type) to 0.175 Å (50% disorder). XRD analyses were performed by the Debye Scherrer method on a goniometer using 1.5418 Å Cu Kα radiation and a Ni filter. The XRD data of the natrolite samples analyzed (JU1-4 and JU1-7N) correspond to the 20-0759 and 19-1185 files of JCPDS Mineral Powder Diffraction File Data Book (Bayliss et al. 1986). Based on this, the cell parameters were calculated for each sample (table 1) and b-a = 0.232 (JU1-4) and 0.183 (JU1-7N). The cell parameters listed in Table 1 indicate that Junin natrolite exhibits 50% Si/Al disorder.Chemical analyses indicated: TSi ≥ 0.63, Si/Al≥1.70, and Ca=0-0.55. This composition combined with the disorder in the structure are indicative of tetranatrolite/Na-rich gonnardite