Phantom quartz

Phantom quartz is a variety of quartz, or "rock crystal", that forms over pre-existing crystals. The included crystal is visible due to some variation in composition making the boundary of the included crystal visible. Such crystals display the outlines of numerous smaller crystals, known as phantoms. Phantom quartz has been found in Austria, Brazil, Madagascar, Switzerland, and the United States.

Like regular quartz, the chemical composition of phantom quartz is silicon dioxide (SiO₂). The available forms of phantom quartz are crystal groups and single crystals used as jewelry pendants.