THE chemical composition of tektites is a major factor to be considered when investigating theories of tektite origin. Many investigators have remarked on the similarity of the composition of tektites to certain types of sedimentary rocks, and this fact has been held to be indicative of a terrestrial origin. Recent determinations1 of the abundances of the alkali elements, lithium, sodium, potassium, rubidium and cæsium in australites showed that a close coherence existed between these five elements in different samples ; in fact, the concentration of one alkali element was shown to be positively correlated with the concentration of any other to a high degree of significance.