Classification of solid inclusions by their time of entrapment

By time of entrapment, solid inclusions are divided into three categories: those formed before the host crystal, called protogenetic; those that form together with the growing crystal, during its formation, called syngenetic; and finally those formed after the host crystal had finished its growth, crystallizing in fissures and as alteration products of previously formed inclusions, called epigenetic. The figure below is a schematic representation of these three types of inclusions. They are considered more in depth in further sections.

Schematic representation of three types of solid inclusions, classified by their time of entrapment, relative to the host crystal.