Summary
The crystal structures of two natural magnetites were refined. Both turned out to have equipoints 8a and 16d (Fd3m) fully occupied and hence different from type I and type II defect structures investigated by Fleet (1981, 1982). It was possible to improve the cation radii for Fe2+ ad Fe3+ in octahedral and tetrahedral coordinations for pure and almost pure magnetites obtaining very good agreement between observed and calculated values of the two independent geometric structure parameters, i.e. cell edge and oxygen coordinate. The present results lead to an estimate of inversion parameter i in (Fe 2+1−i Fe 3+ i )(Fe 2+ i Fe 3+2t-i )O4, of about 0.90, equal for all the four pure magnetites, independently of type of structure and also of cooling history.
Zusammenfassung
Die Kristallstrukturen von zwei natürlichen Magnetiten wurden verfeinert. Es stellte sich heraus, daß ihre Gitterplätze 8 a und 16d (Fd 3 m) voll besetzt sind, und sich somit von den von Fleet (1981, 1982) bestimmten Defektstrukturen unterscheiden. Die Kationradien für Fe2+ und Fe3+ in Oktaeder- und Tetraeder-Koordinationen wurden für reine und fast reine Magnetite verbessert. Dabei wurde eine gute Korrelation zwischen beobachteten und berechneten Werten der beiden unabhängigen Parameter in der Struktur, d.h. Gitterkonstante und Sauerstoff-Ortsparameter gefunden. Die vorliegenden Ergebnisse bringen einen Umkehrparameter i in (Fe 2+1−i Fe 3+ i )(Fe 2+ i Fe 3+2−i )O4 von ungefähr 0.90, der in allen reinen Magnetiten gleich und unabhängig von dem Strukturtyp sowie dem Abkühlverhalten ist.
Similar content being viewed by others
References
Blessing RH, Coppens P, Becker P (1972) Computer Analysis of Step-Scanned X-ray Data. J Appl Cryst 7: 488–492
Della Giusta A, Princivalle F, Carbonin S (1986) Crystal chemistry of a suite of natural Crbearing spinels with 0.15 ⩽ Cr ⩽ 1.07. N Jb Min Abh 155: 319–330
Finger LW, Hazen RM, Hofmeister AM (1986) High-pressure crystal chemistry of spinel (MgAl2O4) and magnetite (Fe3O4): comparisons with silicate spinels. Phys Chem Minerals 13: 215–220
Fleet ME (1981) The structure of magnetite. Acta Cryst B37: 917–920
—— (1982) The structure of magnetite: defect structure II. Acta Cryst B38: 1718–1723
Hafner S (1960) Metalloxyde mit Spinellstruktur. Schw Min and Petr Mitteilungen 40: 208–240
Hamilton WC (1958) Neutron Diffraction Investigation of the 119 K Transition in Magnetite. Phys Rev 110: 1050–1057
—— (1965) Significance tests on the crystallographic R factor. Acta Cryst 18: 502–510
James F, Ross M (1975) A system for function minimization and analysis of the parameter error and correlations. Computer Phys Comm 10: 343–367
Nakagiri N, Manghnani MH, Ming LC, Kimura S (1986) Crystal structure of magnetite under pressure. Phys Chem Minerals 13: 238–244
North ACT, Phillips DC, Scott-Mathews F (1968) A semi-empirical method of absorption correction. Acta Crystallogr A 24: 351–359
O'Neill HStC, Navrotsky A (1983) Simple spinels: crystallographic parameters, cation radii, lattice energies, and cation distribution. Am Min 68: 181–194
——, —— (1984) Cation distributions and thermodynamic properties of binary spinel solid solutions. Am Min 69: 733–753
Shannon RD (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Cryst A 32: 751–767
Trestman-Matts A, Dorris SE, Mason TO (1984) Thermoelectric determination of cation distributions in Fe3O4 - MgFe2O4. J Am Ceram Soc 67: 69–74
Urusov VS (1983) Interaction of cations on octahedral and tetrahedral sites in simple spinels. Phys Chem Minerals 9: 1–5
Wechsler BA, Lindsley DH, Prewitt CT (1984) Crystal structure and cation distribution in titanomagnetites (Fe3−x Ti x O4). Am Min 69: 754–770
Wu CC, Mason TO (1981) Thermopower measurement of cation distribution in magnetite. J Am Ceram Soc 64: 520–522
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Della Giusta, A., Princivalle, F. & Carbonin, S. Crystal structure and cation distribution in some natural magnetites. Mineralogy and Petrology 37, 315–321 (1987). https://doi.org/10.1007/BF01161823
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01161823