Soil dissolved parent rock as a secondary mineral, except when derived from the weathering of mica. It is the surface area to volume ratio (specific surface area) of soil particles and the unbalanced ionic electric charges within those that determine their role in the fertility of soil, as measured by its cation exchange capacity. Sand is least active, having the least specific surface area, followed by silt; clay is the most active. Sand's greatest benefit to soil is that it resists compaction and increases soil porosity, although this property stands only for pure sand, not for sand mixed with smaller minerals
Rock Sand to his best position of second on the list of leading sires. On his four-year-old debut, Rock Sand ran against Sceptre again in June over the Derby course and distance in the Coronation Cup, a race which also featured the first meeting between Rock Sand and his contemporary Zinfandel, a colt whose engagements in the previous year's classics had been rendered void by the death of his owner Colonel Harry McCalmont. Zinfandel won easily from Sceptre, with Rock Sand third. Rock Sand avoided Zinfandel for the remainder of the season and was unbeaten in his remaining five races. He won