Many iron ore and polymetallic deposits are located among volcanic strata, at first glance, completely homogeneous porphyritic composition. When making geological sections of such deposits it is necessary to dissect these homogeneous volcanic strata and to distinguish among them reliable marking layers. The success of the correct interpretation of the structure of the ore field or its separate sections depends to a large extent on how correctly deciphered the sequence of formation of various volcanic layers consisting of porphyritic covers or flows.