This book gives an outline of the world’s literature on analytical info and theoretical strategies of the regularities of infrequent earth parts (REE) in ultramafic and mafic rocks of other 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 normally 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 sorts of massifs, complexes, and provinces. quite a few elements in their intragranular and intermineral distribution are thought of, and knowledge 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 is predicated at the result of analyses of numerous millions of rock samples and greater than 2000 analyses of minerals, a part of which used to be performed with samples from author’s collections. The ebook 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 faculties and post-graduate students.