Iron, coarse octahedrite – IAB-MG; Gran Chaco, Argentina (27°28' S, 60°35' W)

Similar to lot 12. This is a complete slice of a Campo del Cielo meteorite from the same event in Argentina that produced the third and fourth most massive meteorites on Earth — 30.8 and 28.8 tons.

The latticework seen is referred to as a Widmanstätten pattern (see lot 45) and is a product of the intergrowth of the two iron-nickel alloys typically present in meteorites: kamacite (a low-nickel variety) and taenite (a high-nickel variety).

Slow cooling, lasting millions of years, was required for these two iron-nickel alloys to crystallize. As such a circumstance would not exist anywhere on Earth except in the core, the presence of such a crystalline structure is diagnostic in the identification of iron meteorites. The pattern variations reflect the different compositions of the parent body from which the meteorite originates (see lots 10, 18 and 19). In general, the higher the percentage of nickel content, the finer the pattern — up to about 13% nickel; beyond that point an octahedral structure rarely occurs. This specimen is delimited by the external surface of the meteorite from which it was cut. An elongated spindle of schreibersite accents the highly robust lattice.

Christie's would like to thank Dr. Alan E. Rubin at the Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles for his assistance in preparing this catalogue.

141 x 131 x 3mm (5.5 x 5 x 0.1 in.) and 304.8g (0.66 lbs)