The inorganic fraction is divided into three classes, defined by particle size (1 mm = 0.04 inch): Sand particles have a diameter between 0.02 and 2 mm, silt ranges from 0.002 to 0.02 mm, and clay particles are smaller than 0.002 mm. Mixtures of sand, silt, and clay are called loams; a sandy-loam, for example, contains proportionately more sand. In humus-loams various proportions of organic matter are mixed with the other components.
