ABSTRACT

An investigation has been undertaken of the sieving of natural heavy-mineral sands from a beach placer to determine the effects of the differing shapes of the several mineral types. The measurements agree with an equation derived by Sahu (1965) based on the passage of ellipsoidal grains through a square-sieve opening demonstrating that the ratio of the grain's smallest axial diameter (D_c) to its intermediate diameter (D_b) controls grain passage through the sieves. Empirical relationships are established between the average D_b values of the grains and the sieve size on which they are captured during sieving. These relationships are sufficiently close to that for quartz grains to conclude that there would be little separation of the several minerals by s ape during the sieving process. The results further permit evaluations of the D_b, distributions of the heavy-mineral sands rather than the standard practice of reporting distributions in terms of sieve sizes.