Soil minerals are the inorganic part of soil matter, i.e. the weathering products of volcanic, worked or sedimentary rocks, as well as the compounds formed during soil formation.
The sorptive properties of soil minerals are determined by the nature of their crystalline structure. The minerals of greatest value from the point of view of agricultural chemistry are those forming packets, separated by spaces of different dimensions, on which depends the possibility of sorption of different cations and the tendency to swell in water. These include kaolinite, chlorite, vermiculite, as well as smectite, illite and oxides and hydrated metal oxides, which are dominant in Polish soils.
From the point of view of correct air-water relations, it is not only the crystalline structure of the soil minerals that is important, but also to a large extent the porosity of the soil, which ranges from around 30% to as much as 90% (for most plants, the optimum value is 50-60%). Porosity depends primarily on the size of the mineral grains.
The rules for the designation and classification of soils in Europe are specified in EN ISO 14688-1:2006 (EN ISO 14688-1:2002).