Magnetischer Entwickler, Prozesskassette und Bildherstellungsverfahren

A magnetic toner is formed from a binder resin and silicon-containing magnetic iron oxide particles. The magnetic toner has a weight-average particle size of at most 13.5 mu m, and the magnetic toner has a particle size distribution such that magnetic toner particles having a particle size of at least 12.7 mu m are contained in an amount of at most 50 wt. %. The magnetic iron oxide particles have a silicon content of 0.4 - 2.0 wt. % based on iron, and the magnetic iron oxide particles have an Fe/Si atomic ratio of 1.2 - 4.0 at the utmost surfaces thereof. Because of the use of such magnetic iron oxide particles having a specifically controlled overall and surface Si contents, the magnetic toner can show stable performances even after standing in a high humidity environment.