Phantoms versus Inclusions
A true Phantom is a crystal that forms over another crystal!
The outline of the original crystal is visible inside and is not to be confused with interior fractures or other inclusions of minerals captured during it's growth.
Pretty cool, huh?!
Included (Inclusion) is when material is trapped inside a mineral while it was being formed. An Inclusion is not a Phantom.
Commonly known Included Quartz are Rutilated Quartz (Needle-like rutile inclusions) and Tourmalinated Quartz. (Inclusions of Tourmaline)
And then there's Quartz with bubbles and fractures within the crystal itself. Often a fracture will create a rainbow effect when viewing from varying angles.