INVESTIGADORES
GALLISKI Miguel Angel
congresos y reuniones científicas
Título:
Reddingita (Mn2+ Fe2+)3 PO4)2 . 3 H2O del yacimiento Ranquel, Distrito Pegmatítico Totoral, San Luis, Argentina.
Autor/es:
OYARZÁBAL JULIO CÉSAR; GALLISKI MIGUEL ANGEL
Lugar:
La Plata
Reunión:
Congreso; XVI Congreso Geólogico Argentino; 2005
Institución organizadora:
Asociación Geológica Argentina-Universidad Nacional de La Plata
Resumen:
Reddingite, a member of the phosphoferrite-reddingite series, has been found in the beryllium-bearing Ranquel pegmatite, belonging to the Loma Alta group of the Totoral pegmatitic field, San Luis, Argentina. This phosphate mineral occurs as fine-grained compact aureoles and pseudo-octaedral crystals lining altered triphylite-graftonite nodules. Reddingite is reddish brown, has a vitreous to resinous luster, a Mohs hardness of 3.5 and a density of 3.252 g/cm3. Optically it is transparent, biaxial (+), 2Vγ ~ 55º, with X pale brown, Y reddish brown and Z greenish brown, α 1.650, β 1.656, γ 1.679, δ 0.029. The five strongest X-ray powder-diffraction observed lines [d in Å(I)(hkl)] are: 3.20(100)(202), 2.734(70)(230), 1.971(70)(323), 2.347(60)(141) and 5.01(50)(020). The unit-cell dimentions data, derived from the least squares refinement, are: a 9.525(3) Å, b 10.094(3) Å, c 8.710(3) Å, V 837.415 Å3. The chemical composition, based on EDS X-ray and TGA analyses give P, Mn, Fe and Mg (Mn:Fe ~ 1:0.62 and Mn:Mg ~ 1:0.09) as main components, and ~ 3H2O. Reddingite has been formed by alkali leaching and hydrothermal reworking of primary triphylite under no-oxidative conditions.
