A method of separating a mixture of solid materials includes supplying a stream of a mixture of solid materials to a stationary inclined surface and collecting a plurality of particles at one or more collection ports spaced from and located along the axis of the inclined surface. The mixture of solid materials includes a plurality of particles. The plurality of particles includes rubber particles and plastic particles. The particles of the mixture contact the stationary inclined surface and travel downward along the surface due to gravitational force. The collected particles include a higher percentage of the rubber particles than mixture due to a greater degree of bouncing of the rubber particles due to their higher friction compared with plastic particles. A material sorting apparatus includes a stationary inclined surface, a feeder, and a plurality of collection ports spaced from and located along the axis of the inclined surface.