Hostname: page-component-77c89778f8-rkxrd Total loading time: 0 Render date: 2024-07-18T22:39:45.821Z Has data issue: false hasContentIssue false

Yttrotungstite

Published online by Cambridge University Press:  05 July 2018

R. J. Davis
Affiliation:
Mineralogy Department, British Museum (Natural History), Cromwell Road, London, S.W. 7
G. W. Smith
Affiliation:
British Petroleum Co. Ltd., B.P. Research Centre, Sunbury-on-Thames, Middlesex

Summary

Yttrotungstite occurs at Kramat Pulai mine, and at Tapah, Kinta, Perak, Malaysia, as yellow earthy material and as monoclinic laths, elongated along [001], flattened, and always twinned, on {100} to pseudo-orthorhombic symmetry, and frequently bevelled by {110}; crystals are very rarely terminated by {101}. γ = [010], α:[001] = 26°, probably in β acute, and 2Vα ≃ 68°. A thermal weight loss curve and an infra-red absorption spectrum are given and discussed. Accessory minerals include raspite and stolzite.

The yttrotungstite unit cell has a 6·95, b 8·64, c 5·77, β 104° 56′, space group P21/m; cell contents are (Yt, Ln, Ca, Mg)2(W, Al, Si, Ti, Fe)4(O, OH)14(OH)2·2H2O. Indexed X-ray powder data are given. Microprobe studies show that Al and Si replace W and are concentrated in zones showing larger values of a sin β (6·75 Å instead of 6·72 Å) but with no other appreciable difference in cell dimensions. Crystal structure studies show that the structure consists of WO6 octahedra sharing non-opposite edges in zig-zag chains running parallel to [010]. Yttrium is in approximately trigonal prismatic coordination between the chains, with the water molecule as a seventh neighbour at one prism face. The water molecule is accommodated in the angle between zig-zags in the WO6 chains; it is probably hydrogen bonded to chain oxygen atoms, and becomes coordinated to the yttrium by a shear between chains away from strict close-packing of the oxygen atoms. The shear is related to the change in a sin β in (Al, Si)-rich zones; arguments based on this and on details of the chemical analysis suggest that SiO4 replaces WO6 with a local oxygen deficit.

Oxygen atom peaks on partial Fourier difference syntheses for our data for yttrotungstite are only slightly larger than the troughs in the syntheses due to experimental error. Methods of testing the significance of the positive peaks are described in an appendix.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1971

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

Beard, (E.H.), 1950. Colon. Geol. Min. Resources. 1, 50-1.Google Scholar
Bradford, (E.F.), 1961. Proc. Pacific Sci. Congr (Ninth Congress, 1957), 12, 378-98, esp. 380-I, 386- 7 .Google Scholar
Butler, (J.R.), 1957- Geochimica Acta. 12, 190-4.CrossRefGoogle Scholar
Dunning, (A.J.) and Vand, (V.), 1969. Acta Cryst. A25, 489-91.CrossRefGoogle Scholar
Farquhar, (M. C. M.) and Lipson, (H.), 1946. Proc. Phys. Soc. 58, 200-6.CrossRefGoogle Scholar
Hamilton, (WALTER C.), 1965. Acta Cryst. 18, 502-10.CrossRefGoogle Scholar
Hess, (J.B.), 1951. Ibid. 4, 209-15.Google Scholar
Jones, (L.H.), 1954. Journ. Chem. Physics. 22, 217-19.CrossRefGoogle Scholar
Lyon, (R. J. P.), 1962. Nature. 196, 266-7.CrossRefGoogle Scholar
Quenouille, (M.H.), 1952. Associated Measurements (Butterworths, London).Google Scholar
Scrivenor, (J.B.) and Shenton, (J.C.), 1927. Amer. Journ. Sci. ser. 5. 13, 487-90.CrossRefGoogle Scholar
[Semenov, (E. I.), Kataeva, (Z. T.), and Rudnitskaya, (E. S.)] (Compt. Rend. Acad. Sci. URSS), 163, (2) 447-9 (English trans. Dokl Acad. Sci. USSR (Earth Sci. Sect.), 163, (2) 103-5).Google Scholar
Smith, (J.V.) and Bailey, (S.W.), 1963. Acta Cryst. 16, 801-11.CrossRefGoogle Scholar
[Stishov, (S. M.) and Belov, (S. V.)] (Compt. Rend. Acad. Sci. URSS), 143, (4), 951-4. (English trans. Dokl. Acad. Sci. USSR (Earth Sci. Sect.), 1964, 143143, 146-8).Google Scholar