Chemical and mineralogical compositions of cosmic and terrestrial spherules from a marine sediment.

The mineralogical and chemical compositions and the specific gravities were determined for particles in a collection of large (149-351 μ diameter), dense, magnetic spherules separated from 750 kg of Pacific red clay sediment. These spherules were found to fall into one of two categories: (1) a group of high specific gravity composed of magnetite and, in some cases, wustite and α iron with low manganese; and (2) a group of low specific gravity with high manganese. The concentrations, of iridium and nickel in the spherules of the first group are consistent with an iron meteoritic origin, and these are identified as cosmic spherules. The second group is assumed to be terrestrial in origin. Nondestructive measurements were made on individual particles. The requirement that the results of these measurements correlate with one another constitutes a more definitive criterion than those used in the past for establishing the extraterrestrial origins of individual particles.