Grain Shape (1)

Fine soil particle shape depends solely on the type of mineral. Quartz, lime and dolomite are normally cubical, whereas clay minerals are flat, and halloysites (phyllosilicates) are oblong.

Coarse soil particle shape and roughness depend on the type of rock as well as the individual history of transportation and weathering. A longer transport duration results in rounded edges and smoothed out particles. Weathering can also influence the particle roughness.

In the case of coarser fractions, both the particle shape (geometric form) and degree of roundness are described. Generally, the terms that are used in the table are only applied for gravel or coarser material.