Hostname: page-component-cd9895bd7-hc48f Total loading time: 0 Render date: 2024-12-23T16:20:11.440Z Has data issue: false hasContentIssue false
  • English
  • Français

The crystal structure of perhamite

Published online by Cambridge University Press:  05 July 2018

S. Mills ,
G. Mumme ,
I. Grey  and
P. Bordet
S. Mills
Affiliation:
Museum Victoria, GPO Box 666E, Melbourne Victoria 3001, Australia
G. Mumme
Affiliation:
CSIRO Minerals, Bayview Avenue, Clayton, Victoria 3169, Australia
I. Grey*
Affiliation:
CSIRO Minerals, Bayview Avenue, Clayton, Victoria 3169, Australia
P. Bordet
Affiliation:
CNRS Laboratoire de Cristallographie, BP 166X, 38042 Grenoble, France
*
*E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

The crystal structure of perhamite, (Ca,Sr)3Al7.7Si3P4O23.5(OH)14.1 8H2O, from the Emmons mine, Maine, USA, has been determined using single crystal X-ray data. The average structure has trigonal symmetry, Pml, with cell parameters a=7.021(1) Å and c = 20.218(1) Å. It was refined to R1 = 0.044 for 618 observed reflections. The structure comprises ordered blocks of crandallite-type structure, centred at z = 0, intergrown parallel to (001) with disordered aluminosilicate structure blocks centred at z = 1/2 to form a microporous structure containing large channels along [100]. These channels are bounded by 8-member rings of 6 tetrahedra (2 SiO4, 2 A1O4 and 2 PO4) and 2 A1O6 octahedra. Calcium atoms and water molecules are distributed in the [100] channels. A model was developed for the local ordering of silicon into the fractionally occupied sites in the (001) layer at z = 1/2 and this model was refined in space group P321 to R1 = 0.041 for 933 observed reflections. The dominant contributors to the local order are Si3O9 rings of corner-shared tetrahedra, together with Si2O7 pairs of tetrahedra. These units corner-link to (Al,Si)O4 tetrahedra above and below the plane at z = 1/2 to form 4-member rings, which in turn corner-share to PO4 tetrahedra in the crandallite blocks to give the 8-member rings. The analysis suggests that 5-coordinated Si may also be present in the (001) plane at z = 1/2.

Keywords

crystal structureperhamiteMaineUSAXRD
Type
Research Article
Information
Mineralogical Magazine , Volume 70 , Issue 2 , April 2006 , pp. 201 - 209
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2006

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

Alberti, A., Sacerdoti, M., Quartieri, S. and Vezzalini, G. (1999) Heating-induced phase transformations in zeolite brewsterite: new 4- and 5-coordinated (Si,Al) sites. Physics and Chemistry of Minerals, 26, 181–186.CrossRefGoogle Scholar
Altomare, A., Burla, M.C., Camalli, M., Cascarano, G.L., Giacovazzo, C., Guagliardi, A., Moliterni, A.G.G., Polidori, G. And Spagna, R. (1999) SIR97: a new tool for crystal structure determination and refinement. Journal of Applied Crystallography, 32, 115–119.CrossRefGoogle Scholar
Angel, R.J., Ross, N.L., Seifert, F. and Fliervoet, T.F. (1996) Structural characterisation of pentacoordinate silicon in a calcium silicate. Nature, 384, 441–443.CrossRefGoogle Scholar
Blount, A.M. (1974) The crystal structure of crandallite. American Mineralogist, 39, 41–47.Google Scholar
Brese, N.E. and O'Keeffe, M. (1991) Bond-valence parameters for solids. Acta Crystallographica, B47, 192–197.CrossRefGoogle Scholar
Dunn, P.J. and Appleman, D.E. (1977) Perhamite, a new calcium aluminium silico-phosphate mineral, and a re-examination of viseite. Mineralogical Magazine, 41, 437–442.CrossRefGoogle Scholar
Kato, T. (1971) The crystal structures of goyazite and woodhouseite.. Neues Jahrbuch fur Mineralogie Monatshefie, 54–58.Google Scholar
Mills, S. (2003) A note on perhamite from the Moculta (Klemms) phosphate quarry, South Australia. Australian Journal of Mineralogy, 9, 43–45.Google Scholar
Sheldrick, G.M. (1997) SHELX-97. Programs for. Crystal Structure Determinations and Refinement. University of Goettingen, Germany.Google Scholar