Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Krivovichev, S. V. Articles by Menshikov, Y. P. Search for Related Content GeoRef GeoRef Citation

Cafetite, Ca[Ti₂O₅](H₂O): Crystal structure and revision of chemical formula

¹ Department of Crystallography, St. Petersburg State University, University Embankment 7/9, St. Petersburg 199034, Russia
² Geological Institute, Kola Science Centre, Russian Academy of Sciences, Fersmana 14, 184200-RU Apatity, Russia
³ Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, Indiana 46556-0767, U.S.A.

Correspondence: ^* E-mail: sk{at}min.uni-kiel.de

The crystal structure of cafetite, ideally Ca[Ti₂O₅](H₂O), (monoclinic, P2₁/n, a = 4.9436(15), b = 12.109(4), c = 15.911(5) Å, ß = 98.937(5)°, V = 940.9(5) ų, Z = 8) has been solved by direct methods and refined to R₁ = 0.057 using X-ray diffraction data collected from a crystal pseudo-merohedrally twinned on (001). There are four symmetrically independent Ti cations; each is octahedrally coordinated by six O atoms. The coordination polyhedra around the Ti cations are strongly distorted with individual Ti-O bond lengths ranging from 1.743 to 2.223 Å (the average <Ti-O> bond length is 1.98 Å). Two symmetrically independent Ca cations are coordinated by six and eight anions for Ca1 and Ca2, respectively. The structure is based on [Ti₂O₅] sheets of TiO₆ octahedra parallel to (001). The Ca atoms and H₂O groups are located between the sheets and link them into a three-dimensional structure. The structural formula of cafetite confirmed by electron microprobe analysis is Ca[Ti₂O₅](H₂O), in contrast to the formula (Ca,Mg)(Fe,Al)₂Ti₄O₁₂.4H₂O suggested by Kukharenko et al. (1959). The wrong chemical formula suggested for cafetite by Kukharenko et al. (1959) is probably due to admixtures of magnetite or titanomagnetite in their samples. Cafetite is chemically related to kassite, CaTi₂O₄(OH)₂, but differs from it in structure and structural formula.

This article has been cited by other articles:

				S. V. Krivovichev, V. N. Yakovenchuk, G. Yu. Ivanyuk, Y. A. Pakhomovsky, T. Armbruster, and E. A. Selivanova THE CRYSTAL STRUCTURE OF NACAPHITE, Na2Ca(PO4)F: A RE-INVESTIGATION Can Mineral, August 1, 2007; 45(4): 915 - 920. [Abstract] [Full Text] [PDF]

				T. Armbruster, S. V. Krivovichev, T. Weber, E. Gnos, N. N. Organova, V. N. Yakovenchuk, and Z. V. Shlyukova Origin of diffuse superstructure reflections in labuntsovite-group minerals American Mineralogist, November 1, 2004; 89(11-12): 1655 - 1666. [Abstract] [Full Text] [PDF]

				S. V. Krivovichev, S. V. Krivovichev, and T. Armbruster The crystal structure of jonesite, Ba2(K, Na) [Ti2(Si5Al)O18(H2O)](H2O)n: A first example of titanosilicate with porous double layers American Mineralogist, February 1, 2004; 89(2-3): 314 - 318. [Abstract] [Full Text] [PDF]

				I. E. Grey, I.E. Grey, W.G. Mumme, I.V. Pekov, and D.Yu. Pushcharovsky The crystal structure of chromian kassite from the Saranovskoye deposit, Northern Urals, Russia American Mineralogist, August 1, 2003; 88(8-9): 1331 - 1335. [Abstract] [Full Text] [PDF]