The results of the studies of the KMA Prioskolskoye Deposit ferruginous quartzites optical-mineralogical specialties and processing properties are presented. A significant inhomogeneity of properties of the main ore mineral - magnetite is shown. Magnetite crystal lattice defectiveness is ascertained, as well as its composition variability, peculiar magnetic properties (magnetic rigidity), mineral coefficient of inhomogeneity. The necessity of taking into consideration magnetite composition and properties during processing, and, especially, as regards the choice of ore-preparation method, is noted.