Ore mining and processing dumps are open and technogenic systems, which change intensively with time under the influence of environmental factors. Active transformations of such “technogenic deposits” are in close relationship with environmental factors. The purpose of this paper is to determine the nature and causes of the electrical resistivity (ER) changes in the mine tailings dump over time. The investigations were carried out by the method of electrotomography by determining the ER of the section to a depth of 1.5 m with an interval of one hour during the day with simultaneous recording of the substance temperature at a depth of 0.1 m. The maximum daily ER dynamics is observed over intensely transformed technogenic ores. ER is in a numerical relationship with the temperature of the solid matter by an exponential law with a certainty of 96%. A direct dependence of the ER daily changes amplitude on the cementation index m was revealed with the help of the Archie law. The primary material of the heap has a monodisperse composition and small values of m, so the amplitude of the ER dynamics is minimal. As a result of oxidative transformations, the solid matter of the dump becomes polydisperse, which is reflected in the cementation index and the amplitude of the ER daily oscillations increase.