As a result of investigation of biotites from massifs of Obskoy, Novosibirskiy, Kolivanskiy, Barlakskiy of Novosibirskoye Priobye, it is shown, that the greatest differences under the conditions of biotites formation appeared at the temperature of their crystallization, alluminiferousity, alkalinity, ferruginosity. The biotites alluminiferousity is a good criterion of potassium chemical activity (alkalinity) in melts, and ferruginosity is a criterion of granitoids crystallization temperature. The granitoids of examined intrusives according to their alluminiferousity are divided into three groups of alkalinity (tab.1) and two temperature groups. In the process of rock formation of Obskoy, Novosibirskiy, Mochishche massifs, the successive increase of micas ferruginosity component up to siderophyllite composition at a relatively identical alluminiferousity and high activity of potassium (alkalinity) take place. A certain decrease of alkalinity is registered under the crystallisation of limit differentiates (Barlakskiy massif).