Are carbonaceous chondrites primitive or processed - A review

According to the results of the present analysis, carbonaceous chondrites are obviously not pristine samples of proto-solar-system condensates. In terms of chemistry, however, these chondrites may represent the most primitive solar system materials known. It appears that the alterations experienced by carbonaceous chondrites were isochemical, or nearly so, so that their bulk compositions have remained practically unchanged, provided that the analyses are representative of large portions of the meteorites.