The [9]-coordinated X site in the crystal structure of tourmaline-group minerals
- Author(s)
- Andreas Ertl, Ekkehart Tillmanns
- Abstract
The [9]-coordinated X site in tourmaline is usually occupied by Na, Ca, K, or is vacant. In contrast to earlier statements in the literature our recent evaluation of 81 tourmaline samples with Al on the Z site has clearly shown that the distance, as could have been expected, is pos. correlated to the av. effective ionic radius of the X-site occupants (r = 0.98 for 81 tourmaline samples, with Al6 at the Z site and (OH)3 at the V site). Olenite and "oxy-rossmanite" samples, in which the V site is not completely occupied by OH, show a significant deviation to this correlation. X-site vacancies (up to ~0.7 apfu), as well as a significant variation of and distances, do not seem to have a significant effect on the distance. Tourmalines of the elbaite-olenite-rossmanite series (with Al6 at the Z site) show a pos. correlation between the and the distance (r = 0.80; 40 samples) due to inductive effects in the structure.
- Organisation(s)
- Department of Mineralogy and Crystallography
- Journal
- Zeitschrift für Kristallographie - Crystalline Materials
- Volume
- 227
- Pages
- 456-459
- No. of pages
- 4
- ISSN
- 2194-4946
- Publication date
- 2012
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105113 Crystallography, 105116 Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/4a1a93aa-89ee-44f5-965a-13fd716c0f7b