inclusions in a marquise shaped piece of quartz



In mineralogy an inclusion is any material that becomes trapped within a rock or a mineral during its formation.  In gemmology it's a characteristic that's either enclosed within a gemstone or which reaches the surface from the inside.

Although inclusions are usually other minerals they may also be water, gas or petroleum and in the case of amber, they're insects or plants.  Inclusions are one of the most important factors when determining a gemstone's value and whilst in some they affect clarity hence the value diminishes, in others such as star rubies and sapphires and varieties of included quartz the inclusions are the very reason why the value increases.