Abstract: A method and apparatus for separating ferrous particles from crushed siliceous slag and for providing successive size gradations of the siliceous material. Particles of the raw slag are introduced into a rotary receptacle including an upstanding side wall which defines a series of apertures having radially disposed axes. As the receptacle rotates, the particles are centrifugally projected into a magnetic field to separate the ferrous particles from the silica and to withdraw the ferrous particles onto a nonmagnetic belt-type carrier. The siliceous particles are projected by the receptacle over different distances proportional to their masses and are collected in successive cylindrical receiving bins concentric with the receptacle's axis of rotation. In some embodiments the separating operation takes place within an enclosure which is maintained at subatmospheric pressure.