MODEL FOR THE QUANTITATIVE ESTIMATION OF MINERAL LIBERATION BY GRINDING

An exact expression is derived for the fraction of particles of mesh size D that contain less than a prescribed fraction of any particular mineral. The expression is obtained entirely in terms of the distributions of linear intercept lengths of the minerals in the ore. These distributions can be obtained by line traverses across a section of the ore. No other statistical information regarding the mineral grain sizes is required. The theory is completely free of empirical constants or other parameters and in particular no assumptions are made regarding the shape of the mineral grains in the ore or of the particles. The theory predicts that the fractional liberation of mineral at mesh size D is given by: L(D)=1- 1 μ ∫ 0 Du {1-N( l D)} {2-F(l)}dl where F(l) is the distribution of linear intercept lengths for the mineral and μ is the mean linear intercept length for the mineral. N(l/D) is the linear intercept distribution function for particles of mesh size D and Du is the largest intercept length across any particle of mesh size D. The theory was confirmed experimentally for the liberation of pyrite from Witwatersrand quartzite. © 1979.