Thermomagnetic analysis of meteorites, 1. C1 chondrites

Samples of all five of the known C1 chondrites have been analyzed thermomagnetically. The only magnetic phase found in four of the chondrites (Alais, Ivuna, Orgueil, Tonk) was magnetite containing less than 6% nickel. The Revelstoke C1 chondrite contains essentially Ni-free Fe₃O₄ as the predominant phase; however, a small amount of a thermally unstable iron compound (presumably FeS) is additionally present. Estimates of the weight percentage of magnetite, based on saturation moments, are: Alais, 5.3 ± 0.4%; Ivuna, 12.2 ± 0.9%; Orgueil, 11.9 ± 0.8%; Revelstoke, 7.2 ± 0.5%; and Tonk, 9.4 ± 0.6%. The first three estimates are based on multiple analyses and are considered to be grossly representative of the meteorites as a whole. The last two estimates are based on single-sample measurements and should be considered only in that context. The magnetite of the Alais sample appears to be somewhat unusual inasmuch as it is inhomogeneously distributed, and its content is only about half that of the average C1 chondrite.