Allan Hills A81005: A rare bird

Abstract

A sole, crystalline metal grain about 1 mm in diameter is lodged in a small sample (3×2.5×3 cm) of anorthositic breccia that was collected with other pristine meteorites in the ice floe at Allan Hills, Antarctica. The fascination of sample ALHA81005 is that it is a very unusual anorthositic breccia, the only such meteorite ever found. This breccia sample is composed mostly of Ca‐rich plagioclase, averaging An 97 (range An 95–98), with striking similarity to anorthositic samples collected during the Apollo missions from the lunar highlands. Only time and the results of chemical analyses of major and trace elements will tell whether this is the first meteoritic sample identified from the moon. Meanwhile, in the Antarctic Meteorite Newsletter (Nov. 1982), Brian Mason describes this sample as ‘a very rare bird’ indeed.