Grain size distributions of various materials in an abrasion mill

Abstract

Wet abrasion of sand-sized quartz and orthoclase in polyethylene bottles for 912 hours showed that abrasion of fine material is practically negligible, in agreement with Kuenen (1959). The size distributions of the sand. sized quartz and orthoclase remained unchanged. The size distributions of sand-sized quartz, orthoclase, plagioclase, and hornblende abraded off of pebbles appear to be lognormal by number percentage. There is considerable question as to the accuracy of the method of counting grains. The size distributions of quartz and orthoclase crushed or abraded to sized less than 0.5 mm appears to be lognormal, which is in disagreement with Rogers, Krueger and Krog (1963). Several tentative reasons are given. Roundness and sphericity of both crushed sand-sized quartz and orthoclase and sand-sized quartz and orthoclase abraded off of pebbles increase with time in the abrasion mill, the rate of change being greater for the fine sand sizes than for the coarse sand sizes. One result of the experiments described in this report is the indication that the size distributions of natural materials seem to be determined by the size distributions of the source rocks. This result is the basis for criticism of the concept of tectonic control of grain size distribution used by Cadigan (1961). It is concluded that the processes of abrasion, sorting, mixing with other sediments, etc. are at least as important as tectonic environment in the production of particular size distributions in sediments.