soil texture, describes the size distribution of soil particles (those less than 2 mm diameter), simplified to indicate the proportions of clay, silt, fine, and coarse sand (stones and rocks and organic matter are excluded). The individual constituents are defined below. Soils predominantly of clay are described as heavy textured. Loams are medium-textured soils, normally containing a fairly even balance of clay, silt, and sand. Sands are light-textured soils, often loose and gritty, with a low clay content. Certain mineral elements, most notably calcium, complement textural differences in helping to determine soil friability (see soil structure).