A Two-Phase Intergrowth in Genthelvite from Mont Saint-Hilaire, Quebec
- Calgary
Synchrotron high-resolution powder X-ray-diffraction (HRPXRD) data and Rietveld structure refinement were used to examine a two-phase intergrowth of genthelvite, ideally Zn{sub 8}[Be{sub 6}Si{sub 6}O{sub 24}]S{sub 2}, from the alkaline intrusive complex at Mont Saint-Hilaire, Quebec, where genthelvite occurs in nepheline syenite pegmatites. The structural parameters obtained for the two phases are slightly different from each other. The unit-cell parameters are 8.119190(7) {angstrom} (51% phase 1) and 8.128914(9) {angstrom} (49% phase 2). The refinement gives the chemical formulae and interstitial M cation in terms of Zn and Mn (the Fe content is practically zero) for the Mn-poor genthelvite phase 1 as (Zn{sub 7.8}Mn{sub 0.2}){Sigma}{sub 8}[Be{sub 6}Si{sub 6}O{sub 24}]S{sub 2}, and the Mn-rich genthelvite phase 2 as (Zn{sub 7.0}Mn{sub 1.0}){Sigma}{sub 8}[Be{sub 6}Si{sub 6}O{sub 24}]S{sub 2}. These formulae are comparable to the Mn-poor and Mn-rich phases obtained by electron-microprobe analysis. The intergrowth indicates that diffusion is absent among the interstitial M cations of similar size (Zn{sup 2+}, Fe{sup 2+} and Mn{sup 2+}). Such intergrowths may form under distinct f(O{sub 2}) conditions and probably low temperature of crystallization that inhibits diffusion of M cations.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- OSTI ID:
- 1019145
- Journal Information:
- Can. Mineral., Vol. 48, Issue (5) ; 10, 2010; ISSN 0008-4476
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Two cubic phases in kimzeyite garnet from the type locality Magnet Cove, Arkansas
Crystal Structure of an Anisotropic Pyrope Garnet That Contains Two Cubic Phases