Effect of Grinding on Quartz Particles

Abstract

WHETHER a vitreous or otherwise ‘disturbed’ layer forms on particles of quartz produced by size reduction processes has been the subject of a controversy for some time. In an earlier communication¹ we reported evidence for the absence of a vitreous or mosaic sub-surface layer. A recent paper by Sakabe et al.² leaves little doubt that, in their experiments, a thick vitreous layer was formed by the grinding procedure used. Samples were ground in a, mechanical agate mortar for varying times up to 300 h and fractions of mean particle size of approximately 0.5µ were prepared by centrifuging. Some of their observations are summarized here.