Inclusion is a general name for any small visible foreign matter such as gas, liquid, glass, or mineral enclosed within a gemstone or rock, which is a growth phenomena. Fracture or cleavage in a gemstone are not classed as inclusions. The nature of inclusions are used to indicate the origin of a stone. Inclusions are very helpful in distinguishing synthetic stones from their counterparts.
Ficture1,Inclusions of ruby,photo by guild gem lab.
Some types of inclusions type are: feather, silk, horsetail, veil, fused or treacle, negative crystal, halo, fingerprint, dendrite, centipede, pleochroic halo, zircon halo, two-phase, three-phase, etc.
Inclusions are divided in 4 shapes:
Inclusions may also act as color agent in some gemstones. Presence of inclusions in minerals may caused color such as in quartz and in large number of chalcedony. For example presence of hematite in red variety of carnelian, or chrysocolla is responsible for the green color in greenish blue variety of chalcedony. Or presence of fuchsite inclusions in quartz is responsible for green color in green aventurine or colored clay mineral produce different hues in various types of jasper. Platy green inclusions of chlorite in quartz caused greenish color. Some labradorite feldspars are colored by inclusions of copper.