4. Pedofeatures

They are recognised by a concentration of a grain size fraction related to a mechanical transport.

The most important criteria to describe these textural pedofeatures are: texture and internal fabric

The following classes of particle sizes are proposed to describe textural pedofeatures:

Clay

As a result of their platy habit, the clay particles tend to be oriented parallel to each other. The result is that when they are crossed with the polarised light, the optical phenomena of every individual particle are added to those of the next particle, and the oriented clayey domain acts as if it were a single crystal,

showing different optical properties: interference colour, extinction phenomena,

(the extinction pattern is a measure of the degree of orientation:

good orientation, ,

bad orientation), ),

optical continuity, etc., which make it possible to make interpretations about the atmosphere in which the particles have been distributed, as well as the way they accumulate.

Two types of clay accumulations are distinguished according to their texture:

Limpid clay. This is a uniform clay without inclusions of micro-particles.

Impure clay. Composed of clay that contains fine silt-size particles.

Silt. Consisting of silt-size particles.

Sand. Consisting of sand-size particles.

Clay and silt. Formed of clay- and silt-size particles in variable proportions.

Unsorted. Consisting of variable proportions of sand, silt and clay.