Triangular plot

http://www.ext.colostate.edu/mg/Gardennotes/214.html

A triangular plot represents three variables. In the triangular plot above the three variables that are being represented are clay, silt, and sand. The numbers that run along the triangle represent the percentage for each variable. In the example above it shows that a sandy loam has 10% clay, 60% sand, and 30% silt.