Grain-size distribution of Luna-24 regolith samples

The grain-size distribution in Luna-24 cores has been determined from 1 mm to 40 microns by sieving, and below 40 microns by sedimentation. The distribution is approximately log-normal from 5 to 10 microns, while for smaller sizes the distribution has a surplus relative to the law. Mean particle sizes are 55-79 microns, with standard deviation 1.90-2.42 microns, and a mode in the 50-micron region. One may suggest, based on the grain-size data, that the Luna-24 soil was formed by a mixing of more mature, fine-grained materials with less-reworked, coarser materials.