Abstract

The crystal chemistry of richterite found in two new meteorite occurrences, as well as that of the original richterite found occurring in a meteorite, is presented. Microprobechemical analysis indicates that two of the richterites, from the iron meteorites W ichita County and Canyon Diablo, are not fully fluorinated; however, their a cell param eters suggest they are fully fluorinated. The cell param eters and the chemical analyses arereconciled by postulating that oxygen (O=) substitutes for hydroxyl (OH-) on the O(3)-site. The third richterite, from an enstatite chondrite (A bee), shows α and β parameters lower than those for fully fluorinated richterite. This is attributed to Mg distributed on the M(4)-site, as well as full fluorination, suggesting that a partial solid solution between normal fluorichterite (NaCaNa-Mg5Si8O22F2) and Ca-free fluorichterite (NaMgNaMg5Si8O22F2) may exist in nature. There is no evidence for structural water in any of these meteoritic amphiboles.

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