Granulometric Composition

the content of granules of varying size in rock, soil, or an artificial product, expressed as a percentage of the bulk or of the quantity of granules of the examined sample.

The granulometric composition is an important indicator of the physical properties and structure of a natural or artificial material. Depending upon the research purpose, the granulometric composition can be determined with a varying degree of detail. There is no generally accepted classification for the data of granulometric composition, and this is due to the differing purposes and objects for which the granulometric composition is determined. In geology (lithology), pedology, marine geology, and in technology (abrasives and the dressing of minerals) there are special classifications and names of the granulometric fractions. Thus, in sedimentary rock, the categories are large boulders, over 500 mm; medium-sized boulders, 500–250 mm; small boulders, 250–100 mm; pebbles. 100–10 mm; large gravel, 10–5 mm; small gravel, 5–2 mm; coarse sand, 2–1 mm; large sand, 1–0.5 mm; medium sand, 0.5–0.25 mm; fine sand, 0.25–0.10 mm; silt, 0.10–0.05 mm; dust, 0.05–0.005 mm; and clay, less than 0.005 mm.

The granulometric composition is determined by using granulometric analysis (granulometry). Determining the granulometric composition of fragmentary rock is essential forjudging the rock’s reservoir properties and for discovering under what conditions the rock was formed. The granulometric composition of ground makes it possible to judge its technical properties for construction purposes, while the granulometric composition of soils makes it possible to determine their structural features, which to a significant degree determine soil fertility.