A high temperature in situ single-crystal study of P4/n vesuvianite
Tribaudino, Mario; Prencipe, Mauro
European Journal of Mineralogy Volume 11 Number 6 (1999), p. 1037 - 1042
published: Nov 29, 1999
manuscript accepted: Jun 15, 1999
manuscript received: Sep 24, 1998
ArtNo. ESP147051106012, Price: 29.00 €
Abstract Single crystal X-ray diffraction data were collected at T = 570, 770, 1070 K on a sample of a PA/n vesuvianite from Val d'Ala (Piedmont, Italy). Structure refinements yielded R values of 6.7, 6.8 and 8.5% for the three temperatures, respectively; the PA/n symmetry was retained throughout. The volume thermal expansion coefficient was 33.7(7) · 10-6 K-1; different expansion rates were observed along the a and c directions [10.4(3) · 10-6 K-1 and 12.9(3) · 10-6 K-1 respectively]. The volume expansion is larger than that observed in the structurally similar garnet, due to a higher expansion rate along the c axis. An analysis of the atomic displacement parameters (ADP's) with temperature performed on Ca(2) and Ca(3) atoms did not indicate significant positional disorder. As well no evidence of changes in the cation distribution was found in the Ca(4)a and b and M(2)a and b sites even after prolonged heating at 1070 K.