The crystal skulls are a particularly notable example of the popularization of pseudoarcheological ideas. Some believe the skulls to be of Aztec or Mayan origin, while others think them to be from Atlantis or outer space. 
None of the known skulls are actually from a documented archaeological sites, nor do they reflect the artistic styles of the cultural groups they are attributed to. The first known crystal skull was obtained by the British Museum in 1856 by Henry Christy. At this time there was little known about pre-Columbian artifacts in Mexico and as observed by Smithsonian archaeologist, W. H. Holmes, in 1884 there was an abundance of fake artifacts being sold in Mexico at the time. In 1867 two more crystal skulls surfaced at the Exposition Universelle in Paris. These skulls had been procured by an "archaeologist" named Eugene Boban. Mexico City purchased two crystal skulls; one in 1874 and another in 1886. These skulls account for the first generation of crystal skulls. The second generation of crystal skulls are also associated with Eugene Boban, who in 1881 attempted to sell a crystal skull in his antiques shop in Paris. The skull did not sell so Boban returned to Mexico City in an attempt to sell the skull to Mexico's national museum claiming that it was a genuine Aztec artifact. The Mexican museum declined, however, assuming the skull to be a fake. In 1886 the skull was sold in an Auction in New York to Tiffany & Co. Ten years later Tiffany & Co would sell the crystal skull to the British Museum for the same price it was bought at, $950. The auction's catalog lists another skull having been sold but its current whereabouts are unknown. The third generation of skulls surfaced around 1934 when art dealer, Sidney Burney, purchased a skull with extremely similar proportions to the skull bought by Tiffany & Co. However, this skull was much more detailed and had a detachable mandible. This skull is attributed to the Maya instead of the Aztec, is said to emit a blue glow from its eyes, and is known to occasionally crash computer hard drives.
The popularity of these crystal skulls has greatly increased due to their inclusion in Indiana Jones and the Kingdom of the Crystal Skulls. The popular movie depicts the skulls as belonging to aliens which is a notion deeply rooted in pseudo archaeological thought. 
Tied to Atlantis and also aliens
pop culture and Indiana Jones
Electron Microscope analysis reveal modern tool marks
probs mid to late 1800s
crystal from Brazil or Madagascar and manufactured in Germany
no similar artifacts on real archaeological excavations
- Walsh, Jane MacLaren. "Legend of the Crystal Skulls." Archaeology 61.3 (2008): 36-41.