Hostname: page-component-78c5997874-4rdpn Total loading time: 0 Render date: 2024-11-19T22:00:50.576Z Has data issue: false hasContentIssue false
  • English
  • Français

From structure topology to chemical composition. XIV. Titanium silicates: refinement of the crystal structure and revision of the chemical formula of mosandrite, (Ca3REE)[(H2O)2Ca0.5□0.5]Ti(Si2O7)2(OH)2(H2O)2, a Group-I mineral from the Saga mine, Morje, Porsgrunn, Norway

Published online by Cambridge University Press:  05 July 2018

E. Sokolova  and
F. C. Hawthorne
E. Sokolova*
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
F. C. Hawthorne
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
*
* E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

The crystal structure of mosandrite, ideally (Ca3REE)[(H2O)2Ca0.5☐0.5]Ti(Si2O7)2(OH)2(H2O)2, from the Saga mine, Morje, Porsgrunn, Norway, has been refined as two components related by the TWIN matrix ( 0 0, 0 0, 1 0 1): a 7.4222(3), b 5.6178(2), c 18.7232(7) Å, β 101.4226(6)°, V = 765.23(9) Å3, space group P21/c, Dcalc. = 3.361 g.cm–3, R1 = 3.69% using 1347 observed (Fo > 4σF) reflections. The empirical formula of mosandrite (EMPA) was calculated on the basis of 4 Si a.p.f.u., with H2O determined from structure refinement: [(Ca2.89Ba0.01)Σ2.90(Ce0.39La0.18Nd0.14Sm0.02Gd0.03Y0.16Th0.03)Σ1.01Zr0.09]Σ4 [(H2O)2.00Ca0.32Na0.17Al0.10Mn0.04Fe2+0.02☐0.35]Σ3(Ti0.87Nb0.09Zr0.04)Σ1(Si2O7)2[(OH)1.54F0.46]Σ2[(H2O)1.50F0.50]Σ2, Z = 2. The crystal structure of mosandrite is a framework of TS (titanium silicate) blocks; each TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral). In the TS block, there are five fully occupied cation sites, two [4]-coordinated Si sites with <Si–O> 1.623 Å , [7]-coordinated MH and AP sites occupied by Ca and REE in the ratio ∼3:1, and one [6]-coordinated Ti-dominant MO(1) site. There are two H2O-dominant H2O-alkali-cation sites. The partly occupied MO(2) site has composition [(H2O)0.5☐0.33Na0.17], ideally [(H2O)0.5☐0.5] p.f.u. The MO(3) site has ideal composition [(H2O)1.5Ca0.5] p.f.u. In the O sheet, the XOM and XOA anion sites have compositions [(OH)1.54F0.46] (XOM) and [(H2O)1.50F0.50] (XOA), ideally (OH)2 and (H2O)2 p.f.u. The MH and AP polyhedra and Si2O7 groups constitute the H sheet that is completely ordered. In the O sheet, MO(1) octahedra are long-range ordered whereas H2O and OH groups and alkali cations Na and Ca are long-range disordered. Two SRO (short-range ordered) arrangements have been proposed for the O sheet: (1) Na [MO(2)], Ca2 [MO(3)] and F4[XOM and XOA anion sites]; (2) 2 H2O [MO(2)] and MO(3)] and (OH)2 and (H2O)2 [XOM and XOA]. Linkage of H and O sheets occurs mainly via common vertices of MH polyhedra and Si2O7 groups and MO(1) octahedra. Two adjacent TS blocks are related by the glide plane cy. Mosandrite is an H2O- and OH-bearing Na- and Ca-depleted analogue of rinkite, ideally (Ca3REE)Na(NaCa) Ti(Si2O7)2(OF)F2. Mosandrite and rinkite are related by the following substitution at the MO(2,3) and XO(M,A) sites in the O sheet: M[(H2O)2 + ☐0.5] + X[(OH)–2 + (H2O)2] ↔ M[Na+2 + Ca2+0.5] + X[(OF)3– + (F2)2–].

Keywords

mosandritecrystal-structure refinementEMP analysischemical formulaTi-disilicate mineralsrinkiteGroup I
Type
Research Article
Information
Mineralogical Magazine , Volume 77 , Issue 6 , August 2013 , pp. 2753 - 2771
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2013

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Back, M.E. and Mandarino, J.A. (2008) Fleischer’s Glossary of Mineral Species 2008. The Mineralogical Record Inc., Tucson.Google Scholar
Bellezza, M., Franzini, M., Larsen, A.O., Merlino, S. and Perchiazzi, N. (2004) Grenmarite, a new member of the götzenite-seidozerite-rosenbuschite group from the Langesundsfjord district, Norway: definition and crystal structure. European Journal of Mineralogy, 16, 971–978 CrossRefGoogle Scholar
Bellezza, M., Merlino, S. and Perchiazzi, N. (2009) Mozandrite, structural and crystal-chemical relationships with rinkite. The Canadian Mineralogist, 47, 897–908 CrossRefGoogle Scholar
Brögger, W.C. (1890) Die miniralien der syenitpegmatitga ¨nge der südnorwegischen augit- und nephelinsienite. Zeitschrift fü r Kristallographie und Mineralogie, 16, 74–94 Google Scholar
Brown, I.D. (1981) The bond-valence method: an empirical approach to chemical structure and bonding. Pp. 1–30 in: Structure and Bonding in Crystals II (M. O’Keeffe and A. Navrotsky, editors). Academic Press, New York.Google Scholar
Brown, I.D. and Altermatt, D. (1985) Bond-valence parameters obtained from a systematic analysis of the inorganic crystal structure database. Acta Crystallographica, B41, 244–247 CrossRefGoogle Scholar
Cámara, F., Sokolova, E. and Hawthorne, F.C. (2011) From structure topology to chemical composition. XII. Titanium silicates: the crystal chemistry of rinkite, Na2Ca4REETi (Si2O7)2OF3. Mineralogical Magazine, 75, 2755–2774 CrossRefGoogle Scholar
Christiansen, C.C. and Rønsbo, J.G. (2000) On the structural relationship between götzenite and rinkite. Neues Jahrbuch für Mineralogie Monatshefte, 496–506 Google Scholar
Christiansen, C.C., Johnsen, O. and Makovicky, E. (2003a) Crystal chemistry of the rosenbuschite group. The Canadian Mineralogist, 41, 1203–1224 CrossRefGoogle Scholar
Christiansen, C.C., Gault, R.A., Grice, J.D. and Johnsen, O. (2003b) Kochite, a new member of the rosenbuschite group from the Werner Bjerge alkaline complex, East Greenland. European Journal of Mineralogy, 15, 551–554 CrossRefGoogle Scholar
Fleischer, M. (1958) Rinkite, johnstrupite, lovchorrite and calcium rinkite (all = mosandrite). American Mineralogist, 43, 795–796 Google Scholar
Galli, E. and Alberti, A. (1971) The crystal structure of rinkite. Acta Crystallographica, B27, 1277–1284 CrossRefGoogle Scholar
Lorenzen, J. (1884) Untersuchung einiger Mineralien aus Kangerdluarsuk in Grö nland. Zeitschrift für Kristallographie, 9, 243–254 Google Scholar
Pouchou, J.L. and Pichoir, F. (1985) "PAP" j(r) procedure for improved quantitative microanalysis. Pp. 104–106 in: Microbeam Analysis (J.T. Armstrong, editor). San Francisco Press, San Francisco, California, USA.Google Scholar
Shannon, R.D. (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallographica, A32, 751–767 CrossRefGoogle Scholar
Sheldrick, G.M. (2008) A short history of SHELX. Acta Crystallographica, A64, 112–122 CrossRefGoogle Scholar
Slepnev, Yu.S. (1957) On the minerals of the rinkite group. Izvestiya Akademii Nauk SSSR, Seriya Geologicheskaya, N3, 63–75 (in Russian).Google Scholar
Sokolova, E. (2006) From structure topology to chemical composition. I. Structural hierarchy and stereochemistry in titanium disilicate minerals. The Canadian Mineralogist, 44, 1273–1330 CrossRefGoogle Scholar
Sokolova, E. and Cámara, F. (2007) From structure topology to chemical composition. II. Titanium silicates: revision of the crystal structure and chemical formula of delindeite. The Canadian Mineralogist, 45, 1247–1261 CrossRefGoogle Scholar
Sokolova, E. and Cámara, F. (2008) From structure topology to chemical composition. VIII. Titanium silicates: the crystal structure and crystal chemistry of mosandrite from type locality of Låven (Skådön), Langesundsfjorden, Larvik, Vestfold, Norway. Mineralogical Magazine, 72, 887–897 CrossRefGoogle Scholar
Sokolova, E. and Hawthorne, F.C. (2008) From structure topology to chemical composition. V. Titanium silicates: crystal chemistry of nacareniobsite-(Ce). The Canadian Mineralogist, 46, 1333–1342 CrossRefGoogle Scholar
Wilson, A.J.C. (editor) (1992) International Tables for Crystallography. Volume C: Mathematical, Physical and Chemical Tables. Kluwer Academic Publishers, Dordrecht, The Netherlands.Google Scholar
Supplementary material: File

Sokolova and Hawthorne supplementary material

Structure factors

Download Sokolova and Hawthorne supplementary material(File)
File 72.8 KB
Supplementary material: File

Sokolova and Hawthorne supplementary material

CIF

Download Sokolova and Hawthorne supplementary material(File)
File 56.7 KB