A. gupta, d.s. yan, in mineral processing design and operation, . 12.1. an alkaline slurry from a bauxite grinding mill was scheduled to be classified using a spiral classifier at the underflow rate of t/day. the width of the classifier flight was 1.3 m and the outside diameter of the spiral flights was 1.2.An established concept with new technology: ball mills have been the mills of choice for decades for processing high-grade mineral powders. regardless of whether the material displays mohs hardness values of over 4 or is soft such as limestone or talc, super orion ball mills ensure low-wear and cost-effective.