While it has often been suggested that there are limits to the extent to which particle size can be reduced by comminution, experimental evidence for the existence of such ＇＇grind limits＇＇ is scarce and generally inconclusive. An experimental study of long-lime grinding of crystalline quartz in a stirred-media mill has been carried out with the specific aim of identifying the limit of grinding. Product size distributions have been characterized using a combination of laser diffraction/scattering, centrifugal sedimentation, dynamic light scattering and BET surface area measurement. Qualitative examination of the ground products by transmission electron microscopy has also been performed. The results of the investigation are consistent with a grind limit in the region of 40 to 50 nm for this system. In terms of breakage parameters, it appears that there is a decrease in breakage rates at sizes smaller than about 0.5 mu m and that primary breakage distributions become progressively narrower at submicron sizes.