Optical Microscopy of Meteoritic Metal

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NWA3133 (Metachondrite)

Several stones totaling 4.2 kg were found in the Sahara desert.


NWA3133 is an unusual meteorite. It is highly equilibrated, as shown by the absence of chondrules and a triple junction silicate texture. This meteorite was initially classified as a L7 chondrite, but subsequent work revealed isotopic similarity to CV chondrites. Therefore, NWA3133 may represent extensive equilibration of a CV3 protolith.


Unfortunately, this meteorite is highly weathered with alteration features corresponding to a weathering grade of W3 - W4. The metal particles have been partially to completely replaced by iron hydroxides. Only a few relatively unaltered metal grains are present. This surviving metal consists of zoned taenite associated with some kamacite. In every case, zoned taenite exhibits a clear-etching rim and martensite interior. No taenite cloudy zone structure was observed.