Clay

Clay is a sediment composed of tiny mineral particles that are formed by the weathering and breaking down of rocks and minerals. Clay particles are the smallest inorganic component of soil, measuring no more than 2 µm in diameter. Clay has a low permeability.

Source: GreenFacts

Clay particles are negatively charged and attract positively charged ions (cations). These cations bind to the clay particles but can also be exchanged.

Sedimentary rock(s) - Shale

Boron

Fluoride

Soils degradation