Hostname: page-component-cd9895bd7-fscjk Total loading time: 0 Render date: 2024-12-24T17:12:44.419Z Has data issue: false hasContentIssue false
  • English
  • Français

Diegogattaite, Na2CaCu2Si8O20·H2O: a new nanoporous copper sheet silicate from Wessels Mine, Kalahari Manganese Fields, Republic of South Africa

Published online by Cambridge University Press:  05 July 2018

M. S. Rumsey ,
M. D. Welch ,
A. R. Kampf  and
J. Spratt
M. S. Rumsey*
Affiliation:
Mineral and Planetary Sciences Division, Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
M. D. Welch
Affiliation:
Mineral and Planetary Sciences Division, Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
A. R. Kampf
Affiliation:
Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, USA
J. Spratt
Affiliation:
Image and Analysis Centre, Department of Facilities, Natural History Museum, Cromwell Road, London SW7 5BD, UK
*
* E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

Diegogattaite (IMA2012-096), Na2CaCu2Si8O20·H2O, is a new mineral from the Wessels mine in the Kalahari manganese fields of South Africa. It occurs as a minor phase with other copper-bearing silicates, Cu-rich pectolite, sugilite, quartz, aegirine and undifferentiated Fe-Mn oxides. Diegogattaite is pale turquoise through teal blue. It is found as sub-mm sized grains in a main crystalline patch 3–4 mm in size, and is currently known from only one sample. The mineral is transparent with a vitreous lustre and may have a good cleavage on {001}. It is brittle, with an uneven fracture and a very pale-blue streak. It is non-fluorescent in short- and long-wave UV light and has an estimated Mohs hardness of ∼5–6. Diegogattaite is biaxial (–), α = 1.598(2), β = 1.627(2), γ = 1.632(2); 2Vmeas = 44.0(6)°, 2Vcalc = 44.5°; dispersion: strong r < v, orientation: X = b, Y ≈ ⊥(001), Z ≈ a; pleochroism X colourless << Y ≈ Z blue green. The calculated density is 3.10 g/cm3. Electron-microprobe analysis gave: Na2O 8.07, CaO 7.3, CuO 20.5, FeO 0.36, SiO262.4, H2O(calc) 2.34, total 100.97 wt.%. A charge-balanced formula on the basis of 21 oxygen a.p.f.u. is: Na2.00Ca1.00Cu1.98Fe0.04Si7.99H2O21. Diegogattaite is monoclinic, space group C2/m, a = 12.2439(6) Å, b = 15.7514(4) Å, c = 10.6008(3) Å, β = 125.623(2)°, V = 1661.87(10) Å3 and Z = 4. The five strongest lines in the X-ray powder pattern are [dobs in Å (Iobs)(hkl)]: 4.25(75)(002,22,220), 3.951(77)(040), 3.261(100)(31,13), 2.898(89)(042,03,003), 2.332(66)(331,43,62,260,043). The crystal structure of diegogattaite was determined by single-crystal X-ray diffraction to final agreement indices of R1 = 0.027, wR2 = 0.071 and GoF = 1.090. It represents a completely new silicate topology based upon a double-sheet of SiO4 tetrahedra composed of connected 6482 cages. The structure of diegogattaite is related to those of synthetic nanoporous Na-Cu-Si-O-(OH)-H2O (CuSH) compounds, which are of interest to the solid-state chemistry community as potential ion-exchangers, catalysts and molecular sieves. The structure of diegogattaite forms a bridge between these structures and those of the gillespite-group minerals, including wesselsite. The close spatial association of wesselsite and diegogattaite suggests a possible reaction between them that may point to a synthetic route for the production of novel alkaline-earth-based nanoporous copper silicates.

Keywords

DiegogattaiteNa2CaCu2Si8O20·H2Onew mineralnanoporous sheet silicate6482 cagesynthetic CuSH phasesWessels mineSouth Africa
Type
Research Article
Information
Mineralogical Magazine , Volume 77 , Issue 8 , December 2013 , pp. 3155 - 3162
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

Cunha-Silva, L., Branda˜o, P., Rocha, J. and Almeida Paz, F.A. (2008) The dehydrated copper silicate Na2Cu2Si4O11: a three-dimensional microporous framework with a linear Si-O-Si linkage. Acta Crystallographica, E64, i13–i14.Google Scholar
Fleet, M.E. (1998) Sodium heptasilicate: a high-pressure silicate with six-membered rings of tetrahedra interconnected by SiO6 octahedra: (Na8Si[Si6O18]). American Mineralogist, 83, 618–624.CrossRefGoogle Scholar
Gunter, M.E., Bandli, B.R., Bloss, F.D., Evans, S.H., Su, S.-C. and Weaver, R. (2004) Results from a McCrone spindle stage short course, a new version of EXCALIBR, and how to build a spindle stage. Microscope, 52, 23–39.Google Scholar
Gutzmer, J. and Beukes, N.J. (1996) Mineral Paragenesis of the Kalahari manganese field, South Africa. Ore Geology Reviews, 11, 405–428.CrossRefGoogle Scholar
Kleyenstuber, A.S.E. (1984) The mineralogy of the manganese bearing Hotazel formation of the Proterozoic Transvaal sequence of Griqualand West, South Africa. Transactions of the Geological Society of South Africa, 87, 267–275.Google Scholar
Knight, K.S., Henderson C.M.B. and Clark, S.M. (2010) Structural variations in the wesselsite-effenbergerite (Sr1-xBaxCuSi4O10) solid solution. European Journal of Mineralogy, 22(3), 411–423.CrossRefGoogle Scholar
Mandarino, J.A. (1981) The Gladstone-Dale relationship: Part IV. The compatibility concept and its application. The Canadian Mineralogist, 19, 441–450.Google Scholar
Pozas, J.M.M., Rossi, G. and Tazzoli, V. (1975) Reexamination and crystal structure analysis of litidionite. American Mineralogist, 60, 471–474.Google Scholar
Pouchou, J. L. and Pichoir, F. (1988) A simplified version of the ‘PAP’ model for matrix corrections in EPMA. Pp. 315–318. in: Microbeam Analysis (D.E. Newbury, editor). San Francisco Press, San Francisco, California, USA.Google Scholar
Wang, X., Liu, L. and Jacobson, A.J. (2003) Nanoporous copper silicates with one-dimensional 12-ring channel systems. Angewandte Chemie, International Edition, 42, 2044–2047.CrossRefGoogle ScholarPubMed
Wang, X., Liu, L., Wang, L. and Jacobson, A.J. (2005) Hydrothermal synthesis and structures of the openframework copper silicates Na2[Cu2Si4O11](H2O)2 (CuSH-2Na), Na2[CuSi3O8] (CuSH-3Na), Cs2Na4[Cu2Si12O27(OH)2](OH)2 (CuSH-4NaCs), and Na2[Cu2Si5O13](H2O)3 (CuSH-6Na). Journal of Solid State Chemistry, 7, 1415–1422.Google Scholar
Welch, M.D. and Rumsey, M.S. (2013) A new naturallyoccurring nanoporous copper sheet-silicate with 6482 cages related to synthetic “CuSH” phases. Journal of Solid State Chemistry 203, 260–265.CrossRefGoogle Scholar
Yang, H., Downs, R.T., Evans, S.H. and Pinch, W.W. (2013) Scottyite, the natural analogue of synthetic BaCu2Si2O7, a new mineral from the Wessels mine, Kalahari Manganese Fields, South Africa. American Mineralogist, 98, 478–484.CrossRefGoogle Scholar
Yang, H., Downs, R.T., Evans, S.H., Pinch, W.W. and Origlieri, M.J. (2012) Lavinskyite, IMA2012-028. CNMNC Newsletter No. 14, October 2012, page 1284; Mineralogical Magazine, 76, 1281–1288.Google Scholar
Supplementary material: File

Rumsey et al. supplementary material

CIF

Download Rumsey et al. supplementary material(File)
File 24.8 KB
Supplementary material: File

Rumsey et al. supplementary material

Structure factors

Download Rumsey et al. supplementary material(File)
File 197.2 KB