short note
Triclinic amphibole
Maresch, Walter V.; Miehe, Gerhard; Czank, Michael; Fuess, Hartmut; Schreyer, Werner
European Journal of Mineralogy Volume 3 Number 5 (1981), p. 899 - 904
11 references
published: Sep 25, 1981
manuscript accepted: May 29, 1991
manuscript received: May 13, 1991
DOI: 10.1127/ejm/3/5/0899
Abstract
Abstract Synthetic amphibole with a composition close to Na3 Mg5 [Si8O21/(OH)](OH)2 has been shown by Rietveld refinement of X-ray powder diffraction data to possess triclinic symmetry. Electron diffraction indicates the existence of a superstructure with a three-fold b lattice constant. X-ray powder diffraction at temperatures up to 340°C and differential scanning calorimetry show that the structure transforms reversibly through a complex 60°C transition zone to the common C2/m symmetry above approximately 160°C. We suggest that natural amphiboles, particularly those containing A-sites filled with Na+, should be examined closely for evidence of triclinic symmetry.
Keywords
triclinic amphibole • amphibole superstructure • Rietveld refinement • electron diffraction • X-ray powder diffraction • phase transition