The natural earths are mineral substances provided by nature, they are salts, acids,
sulfides, existing in the soil, in deeper reservoir or shallower reservoir with different types
of stratification and formed since geological era.
This very long geological era gives to these natural earths the peculiar characteristics of
the colour and of the resistance that are intensified by the phases of processing, that can
include the calcination.
Chemical composition: oxides minerals of natural origin (manganese oxides, hematite,
hydrated oxides of iron, celadonite) in different combinations depending on the various
types (on avarage 20-40%)