Sursassite is monoclinic, space Group P21/m, a = 8.70, b = 5.79, c = 9.78 A, beta = 108.9°. The crystal structure was determined with X-rays and refined to R = 0.065, obtaining Mn2Al3[(OH)3(SiO4)(Si2O7)] as ideal crystal chemical formula. Sursassite, isostructural with macfallite Ca2Mn3[(OH)3(SiO4)(Si2O7)], is closely related to pumpellyite Ca2Al3[(OH)3(SiO4)(Si2O7)]. In fact both sursassite and pumpellyite, apart from the different chemical composition, are built up by common structural layers, which are repeated by different stacking vectors. As a result, faulted stacking sequences are energetically possible. Examination by high resolution transmission electron microscopy (HRTEM) shows that frequent (001) pumpellyite-like lamellae are intergrown with thicker sursassite-like lamellae. Usually, the guest lamellae are a few unit cell thick along [001] and continuous along the (001) plane, although also rare interrupted lamellae are found.
X-ray and HRTEM study of sursassite: crystal structure, stacking disorder and sursassite - pumpellyite intergrowth
MERLINO, STEFANO;PASERO, MARCO
1984-01-01
Abstract
Sursassite is monoclinic, space Group P21/m, a = 8.70, b = 5.79, c = 9.78 A, beta = 108.9°. The crystal structure was determined with X-rays and refined to R = 0.065, obtaining Mn2Al3[(OH)3(SiO4)(Si2O7)] as ideal crystal chemical formula. Sursassite, isostructural with macfallite Ca2Mn3[(OH)3(SiO4)(Si2O7)], is closely related to pumpellyite Ca2Al3[(OH)3(SiO4)(Si2O7)]. In fact both sursassite and pumpellyite, apart from the different chemical composition, are built up by common structural layers, which are repeated by different stacking vectors. As a result, faulted stacking sequences are energetically possible. Examination by high resolution transmission electron microscopy (HRTEM) shows that frequent (001) pumpellyite-like lamellae are intergrown with thicker sursassite-like lamellae. Usually, the guest lamellae are a few unit cell thick along [001] and continuous along the (001) plane, although also rare interrupted lamellae are found.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
