Triangular Plot

http://www.dplot.com/triangle-plot.htm

Triangle plots are generally used in the field of geology to show relative composition of soils and rocks. The triangle plot shows the proportions of three variables in this care the variable are silt, clay, and sand. The x variable, which is sand, is measured from 0 to 100 percent with zero being the base of the triangle and 100 being the top of the triangle.  The y variable, which is clay, is measured from 0 to 100 percent with zero being the base, which is on the left side of the triangle and 100 being the point, which is the bottom right side of the triangle.  The z variable which is silt, is measured from 0 to 100 percent with zero being the base which is on the right side of the triangle and 100 being the point which is the bottom left side of the triangle. So a section in the mid left of the triangle would be considered to be made up of a lot of sand and a small amount of clay.