This book gives an summary of the world’s literature on analytical info and theoretical recommendations of the regularities of infrequent earth components (REE) in ultramafic and mafic rocks of alternative chemical and mineral compositions – mantle restites (including these composing mantle xenoliths in alkali basaltoids), hugely magnesium hypabyssal rocks, plutonic rocks of mafic-ultramafic and ultramafic-mafic massifs, in addition to on the whole minerals composing those rocks – olivines, orthopyroxenes, clinopyroxenes, plagioclases, and amphiboles. a lot consciousness is given to a comparative research of the REE distribution in rocks and minerals from types of massifs, complexes, and provinces. a variety of facets in their intragranular and intermineral distribution are thought of, and information at the coefficients in their partition among minerals and their parental melts in addition to among coexisting minerals are generalized. possible schemes of REE isomorphism in rock-forming minerals are mentioned. The generalization relies at the result of analyses of a number of hundreds of thousands of rock samples and greater than 2000 analyses of minerals, a part of which used to be conducted with samples from author’s collections. The booklet is meant for experts in petrology and geochemistry of ultramafic, mafic, and different sorts of igneous rocks in addition to scholars of geological departments of schools and post-graduate students.