Crystal structure of nanlingite - the first mineral with a [Fe(AsO3)6] configuration
- Author(s)
- Zhuming Yang, Gerald Giester, K. Ding, Ekkehart Tillmanns
- Abstract
Nanlingite was first described as a new mineral from a dolomitic limestone along a contact between greisenized granite and dolomitic limestone in the Nanling area, Hunan Province, China. The structure was solved and refined on single-crystal X-ray data in space group R (3) over bar m, with a = 10.2114(10), c = 25.689(3) angstrom, V = 2319.2(6) angstrom(3), to R1 = 0.021, wR2 = 0.049. The chemical formula of nanlingite is Na(Ca, Li, Na)(6)(Mg, Fe)(12)(AsO3)(2)[Fe(AsO3)(6)] F-14 with Z = 3 according to the crystal structure refinement. The complex framework is formed by edge- and corner-sharing of distorted NaF8 and CaF4O4 cubes, MgF2O4 octahedra, and AsO3 trigonal pyramids. The lithium atom occupies (22 %) the split site at 0.58(2) angstrom from the main Ca site and exhibits a five-fold coordination with <Li-(O,F)> 2.21 angstrom. The iron atom (at 3b, site symmetry (3) over bar m) is surrounded by six As atoms of AsO3 groups at a distance of 2.40 angstrom with the lone-pair electrons pointing towards the central atom. This [Fe(AsO3)(6)] cluster is a novel configuration in the crystal chemistry of minerals. According to Mossbauer spectra and electron energy-loss spectroscopy data the oxidation state of Fe in nanlingite is mainly Fe-II with a low-spin state. In the configuration of arsenite groups, the distance <As(2)-O > = 1.73 angstrom of the [Fe(AsO3)(6)] clusters is shorter than the normal range. The empirical crystal-chemical formula for nanlingite is (Na0.90Li0.10) Sigma(1.00)(Ca-4.41 Li-1.06 Mg-0.17 Na-0.06 Mn-0.05 square(0.25))Sigma(6.00)(Mg-11.38 Fe0.303+Al0.29Ti0.03)(Sigma 12.00)(AsO3)(2) [Fe-II(ASO(3))(6)](F13.77OH0.16)(Sigma 13.93).
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- Chinese Academy of Sciences (CAS)
- Journal
- European Journal of Mineralogy: an international journal of mineralogy, geochemistry and related sciences
- Volume
- 23
- Pages
- 63-71
- No. of pages
- 9
- ISSN
- 0935-1221
- Publication date
- 2011
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 1051 Geology, Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/88be700f-a115-4c4a-8f91-252be2442daf