One of the most promising criteria of nickel potential of basic-ultrabasic massifs is naturally considered to be the content in non-ore rocks of nickel, the main component of copper-nickel ores. The main difficulty in applying this criterion is the non-uniformity of the background nickel content, which in the series of basic-ultrabasic rocks increases from the most acidic representatives of the series to the most basic ones. This phenomenon was first taken into account by D. V. Polferov.