Particle diameter (phi scale)
Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithified particles in clastic rocks.
Size ranges define limits of classes that are given names in the Wentworth scale (or Udden-Wentworth) used in the United States. The Krumbein phi (φ) scale, a modification of the Wentworth scale created by W. C. Krumbein is a logarithmic scale.
|ϕ||Diameter of the particle in "phi" (dimensionless)|
|D||Diameter of the particle in "mm" (mm)|
|D0||Reference diameter equal to 1 mm (mm)|