Some people with a mystical bend credit them with strange, supernatural powers. Geologists marvel at their size. Archaeologists wonder who made them. And nobody denies that they possess an eerie, horrible beauty unmatched by almost any other objects. They are the crystal skulls.
There have been many replicas of human skulls that have been polished out of a single crystal of quartz rock. Some are ancient, some contemporary. A few have been made from pure quartz and are absolutely clear. A rare few are also life-sized.

The UnMuseum - Crystal Skulls