The literature on the geochemistry of gallium is very extensive and several problems arise in an attempt to summarise the available information in a short account. Only a small proportion of the many determinations of gallium in rocks and minerals has been made by the most precise and accurate procedures, and ana lyses by emission spectrographic methods constitute a dominant part of the data given here. In Table 31-1 are summarised the results of determinations of gallium in two standard rocks by various procedures. These results show that the generally less precise spectrographic procedures...