They are characterised by a concentration of organic and inorganic materials that are almost isotopes to the polarisation microscope.
They can be subdivided into:
Pure. Formed exclusively of amorphous or cryptocrystalline material, without evidence of pseudomorphic origin.
Pseudomorphic. Formed exclusively of amorphous or cryptocrystalline material that pseudomorphes, partially or completely, mineral, plant or animal remains.
Impregnative. The amorphous or cryptocrystalline material impregnates the soil material or plant remains.
The description is the usual one for pedofeatures and the most important characteristic is the internal fabric, colour and opacity. They are described by their degree of impregnation and their degree of pseudomorphism.
The most frequent are those formed of Fe and
Mn compounds, and by organic materials. The latter are divided
into polymorphic and monomorphic, depending on whether the organic
structures can be distinguished or not.