Gyrolite: its crystal structure and crystal chemistry
The crystal structure of gyrolite from Qarusait, Greenland, was solved and refined with the space group P i and cell parameters a = 9.74(1), b = 9.74(1), c = 22.40(2)A, e = 95.7(1) ~fl = 91.5(1) ~7 = 120.0(1) ~ The structure isbuilt up by the stacking of the structural units already found in the cry...
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
1988
|
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.621.5317 http://www.minersoc.org/pages/Archive-MM/Volume_52/52-366-377.pdf |
| Summary: | The crystal structure of gyrolite from Qarusait, Greenland, was solved and refined with the space group P i and cell parameters a = 9.74(1), b = 9.74(1), c = 22.40(2)A, e = 95.7(1) ~fl = 91.5(1) ~7 = 120.0(1) ~ The structure isbuilt up by the stacking of the structural units already found in the crystal structure of reyerite (Merlino, 1972, 1988), namely tetrahedral sheets $1 and $2 and octahedral sheets O. The tetrahedral nd octahedral sheets are connected by corner sharing to give rise to the complex layer which can be schematically described as $20S~0S2, where $2 and $2, as well as 0 and O, are symmetry-related units. Successive complex layers with composition [Ca14Si23A106o(OH)8]-5 are connected through an interlayer sheet made up by calcium and sodium cations and water molecules. The unit cell content NaCa16Si23A106o(OH)8.14H20, determined by the structural study, was confirmed by a chemical analysis, apart from the indication of a somewhat larger water content. The crystal chemistry of gyrolite is discussed on the basis of the present structural results and the chemical data given in the literature for gyrolite from different localities: the crystal chemical formula which accounts for most gyrolite samples is Ca16Si2406o(OH)8. (14+ x)H20, with 0 ~< x ~< 3. Stacking disorder, twinning and polytypic variants in gyrolite, as well as the structural relationships of gyrolite with truscottite, reyerite, fedorite and the synthetic phases K and Z are described and discussed. |
|---|