Crystal skulls are a metaphor that reality is a consciousness hologram through which we experience virtually. Many of the crystal skulls are tools that awaken human consciousness, referenced by the human brain design of the crystal and the metaphoric eyes.
The crystal skulls are a number of human skull models fashioned from blocks of clear or milky quartz crystal rock, claimed to be pre-Columbian Mesoamerican artifacts by their alleged finders. However, none of the specimens made available for scientific study were authenticated as pre-Columbian in origin. The results of these studies demonstrated that those examined were manufactured in the mid-19th century or later, almost certainly in Europe. Despite some claims presented in an assortment of popularising literature, legends of crystal skulls with mystical powers do not figure in genuine Mesoamerican or other Native American mythologies and spiritual accounts.
The skulls are often claimed to exhibit paranormal phenomena by some members of the New Age movement, and have often been portrayed as such in fiction. Perhaps the most widely known of such portrayals occurs in the film Indiana Jones and the Kingdom of the Crystal Skull. Crystal skulls have been a popular subject appearing in numerous sci-fi television series, novels, and video games.
Sources:
http://en.wikipedia.org/wiki/Crystal_skullhttp://www.cosmicorderingexperience.com/crystal-quartz.html