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Science 4 February 1972:
Vol. 175. no. 4021, pp. 521 - 523
DOI: 10.1126/science.175.4021.521
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Articles

Crystallization Studies of Lunar Igneous Rocks: Crystal Structure of Synthetic Armalcolite

M. D. Lind 1 and R. M. Housley 1

1 North American Rockwell Science Center, Thousand Oaks, California 91360

Crystals of armalcolite, Mg0.5Fe0.5Ti2O5, up to several millimeters in length have been grown from a glass initially having the composition of lunar rock 10017. A single-crystal x-ray study has confirmed that the crystals are isomorphous with pseudobrookite and has shown that the cations are strongly ordered, with the Ti4+ ions occupying the 8f sites and the Fe2+ and Mg2+ ions randomly distributed over the 4c sites. An examination of karrooite, MgTi2O5, has revealed a similar distribution of Mg2+ and Ti4+ ions. A reexamination of earlier x-ray and Mössbauer data for pseudobrookite, Fe2TiO5, has shown that it is more consistent with this type of ordering than with the inverse structure that has been generally assumed.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Cation ordering in MgTi2O5 (karrooite): Probing temperature dependent effects with neutrons.
A. R. Lennie, K. S. Knight, and C. M. B. Henderson (2007)
American Mineralogist 92, 1165-1180
   Abstract »    Full Text »    PDF »
Site disorder revealed through Raman spectra from oriented single crystals: A case study on karooite (MgTi2O5).
H.-P. Liermann, R. T. Downs, and H. Yang (2006)
American Mineralogist 91, 790-793
   Abstract »    Full Text »    PDF »
Thermodynamics and stability of pseudobrookite-type MgTi2O5 (karrooite).
D. Xirouchakis, A. Smirnov, K. Woody, D. H. Lindsley, and D. J. Andersen (2002)
American Mineralogist 87, 658-667
   Abstract »    Full Text »    PDF »


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