Northwest Africa 2924
History: Over 180 kg (several thousand pieces) have been recovered from a small strewn field in Algeria. The largest known piece weighs about 5000 g; most are small pieces that weigh less than 200 g.
Petrography and Geochemistry: (T. Bunch and J. Wittke, NAU) Fine-grained (<0.5 mm) matrix consists of brecciated and partially recrystallized subophitic to granular basalts that enclose larger (up to 2.5 mm) subrounded to subangular olivine (Fa28), pigeonite (Fs31Wo5.4; FeO/MnO = 25.7; Cr2O3 = 0.87, Al2O3 = 1.28 [both wt%]) that rarely shows twinning. These cataclastic basalts contain unusually calcic plagioclase (An99.3) with little FeO (<0.04 wt%); highly twinned pigeonite is compositionally similar to the much larger clast pigeonite (Fs32Wo5.7), but with very little Cr2O3 and Al2O3. Merrillite is also present. Metal blebs (Ni = 6.6 wt%) are irregular in shape and typically <2 mm in size with the exception of metal aggregates and rare, centimeter-size metal nuggets with included pigeonite.
Classification: Mesosiderite; low shock, variable degree of weathering dependent on the specimen size.
Specimens: An 85 g type specimen is on deposit at NAU. Farmer holds a 16 kg sample