THE CARBONACEOUS CHONDRITES—A SELECTIVE REVIEW

The presently known carbonaceous chondrites are listed, and their densities and contents of Fe, Si, and Mg recorded. A review of classification schemes indicate that Wiik's (1956) division into Types I, II, and III reflects basic differences in chemical and mineralogical composition and structure, and is preferable to the Van Schmus-Wood (1967) classification into C1, C2, C3, and C4 types. Renazzo is a Type II meteorite. The Van Schmus division of Type III meteorites into two subtypes is sustained, and is shown to involve not only textural differences but also differences in total iron content. The genesis of the different types of carbonaceous chondrites is ascribed to condensation in different temperature regions within the early solar nebula.