Mineral formations from fumaroles localized in craters and on lava flows were collected by the winter during 1937—1938 eruption of the Klyuchevoskoy volcano (Kamchatka) when a number of adventive craters broke out on its slopes. These were investigated sublimates from craters at different distances from the central core, from their lava flows formed by portions of magma issuing from the core one after another; from flows at various stages of formation and cooling; from fumaroles with wide temperature range. This material allows to get an idea of the distribution of elements in space, time and their depending from temperature. The basaltic magma of the Klyuchevskoy volcano erupted in 1937— 1938 contains the greatest part of the elements Mendeleev’s periodical system, elements characteristic of basic magma as well as those considered as characteristic of acid magma.
During the crystallization of the products of mineral formation from the fumaroles, along with the carrying out of substance from the magma there is taking place an extraction of substance from rocks through which the gases escape, some peculiarities being noticed due to the action of gases of different composition.