Many materials have characteristic angles. Calcite, whewellite, florite, amphibols, and halite are a few examples. This is not to be confused with angularity, the measure of abrasive errosion of a mineral particle.

Calcite has three cleavage planes and one parting plane. As a result, fragments of calcite typically exhibite just a few characteristic angles.

Whewellite is one of three forms of hydrated calcium oxalate. The forms of the crystals are the result of growth patterns rather than cleave. These forms in plant phytoliths are affected by the plant genetics and cell structure. There are a variety of complex forms as a result. The forms seen in the leaves and the bark of the same plant are often different. Tabular forms are easily identified by their uniform interference color over the whole body of the crystal. These tend to show characteristic angles of about 70 and 110 degrees. They are often diamonds or bipyramidal prisms. Other forms of single crystals or twins are just as characteristic. The multiple interference color they exibit demonstrate their three dimensional form. The angles are not as regular in the mount because they don't rest on as uniform a base.