Another widely used classification system is the soil triangle of basic soil textural classes. This naming system is commonly used by the U.S. Department of Agriculture and the U.S. Soil Conservation Service. In this system the relative percentages of three particle size catagories are considered. The three catagories of particles are sand, silt, and clay. The triangular diagram is subdivided into several soil textural classification types, with each soil type comprising a range of percentages of the three particle types. The soil classification type is determined by plotting the percentages of each of the three soil particle classes found within the soil sample on the triangular diagram. The point of intersection of each of these three particle class percentages will fall within one of the soil classification types (see Soil Classification Triangle).
As can be seen by inspection of the triangle, each of the three particle types can vary from zero to 100% of the content of a sediment sample. For example, a 100% clay textural composition would plot at the apex at the top of the triangle. Lesser percentages of clay content would plot somewhere between the top apex and the base of the triangle. The same technique holds true for sand or silt content except that the 100% sand or silt content points are located at the left and right bottom apexes of the triangle respectively. Lesser contents of sand or silt would plot somewhere between the 100% apex and the side of the triangle opposite that apex.
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