Stiff diagram

It is widely used by hydrogeologists and geochemists to display the major ion composition of a water sample.

A polygonal shape is created from four parallel horizontal axes extending on either side of a vertical zero axis.

Stiff patterns are useful in making a rapid visual comparison between water from different sources.

By standard convention, Stiff diagrams are created by plotting the equivalent concentration of the cations to the left of the center axis and anions to the right.

Environmental laboratories typically report concentrations for anion and cation parameters using units of mass/volume, usually mg/L.