Zaisho—A Pallasite Containing Pyroxene and Phosphoran Olivine

Peter R. Buseck*, † and Jim Clark*
* Department of Chemistry Arizona State University, Tempe, Arizona 85287, USA
Department of Geology, Arizona State University, Tempe, Arizona 85287, USA

Abstract: The Zaisho meteorite, one of only four known pallasite falls, contains pyroxene, which is rare in pallasites, and it is only the fourth meteorite known to contain phosphoran olivine. Except for a recent report by Goodrich (1984) such olivine appears to be restricted to pallasites, and to those containing the rare Mg phosphate, farringtonite. It is unique among olivines in having P in tetrahedral sites and having vacancies, for charge balance, in octahedral sites. Zaisho also contains stanfieldite and a phosphate having a composition between that of stanfieldite and farringtonite. Its metallographic cooling rate is similar to that of many other pallasites, but its average olivine composition, Fa18.3, places it in a small group with more Fe-rich olivines than most pallasites.

Mineralogical Magazine; June 1984 v. 48; no. 347; p. 229-235; DOI: 10.1180/minmag.1984.048.347.06
© 1984, The Mineralogical Society
Mineralogical Society (