Crystal skull

Crystal skulls are pieces of quartz carved into skull-like shapes supposedly by Mayans under the supervision of aliens and/or Atlanteans. Supporters of this belief point out that the Mayans would otherwise have lacked the ability to carve these shapes. Detractors point out that there isn't actually a shred of evidence that the Mayans did carve these shapes, and not one has been found by a reputable archaeologist. Instead, they mysteriously pop up whenever cranks investigate old ruins.

Many claims are made about supposed paranormal or supernatural powers exhibited by crystal skulls, but, as you might expect, there is also no evidence for crystal skulls having any properties or uses other than as rather gaudy paperweights - or a launching point for the worst Indiana Jones movie ever.

Wait, what?
While you may have been misled into believing the above text, the crystal skull was actually proved to be an extraterrestrial skull in the fourth, and hopefully final Indiana Jones film, conclusively proving the existence of not only ancient crystal skulls, but also ancient aliens. They may have come from another dimension, but they're still aliens. Oh, and they're (sometimes) magnetic!

The "Real" Skulls
As previously mentioned, most skulls are claimed to be pre-Colombian Mesoamerican artifacts which sat undiscovered until the 19th century. However, as more skulls were found, investigations were done to determine their exact origin. The results won't surprise you if you've been reading this article: they are all fake. This was determined by researchers in two ways: one, by examining the details of the skull and determining that the details and methods of carving could not have been done by Mesoamericans, as they did not have sufficient tools; and two, by examining the chlorite inclusions, which revealed that the very quartz the skulls are made of is only found in Brazil and Madagascar. Many of the existing skulls came from a workshop in Germany and used this Brazilian quartz. Skulls such as these ones were often distributed by art dealers; in fact, the Mitchell-Hedges skull, arguably the most famous existing crystal skull (other than the Indiana Jones one), did not come from a temple in Belize as was claimed by Anna Mitchell-Hedges, but was acquired from London art dealer Sydney Burney (though how he got it remains a mystery). Mitchell-Hedges alleged that she found the skull while at an expedition with her father F.A. Mitchell-Hedges in 1924, and that it had magic powers; the skull, nor Anna's presence, are mentioned in Mitchell-Hedges' notes, which is telling. Additionally, a letter to Mitchell-Hedges' brother in 1943 details that he got the skull from Burney at a Sotheby's auction.

Despite this, the authenticity remained unknown. Frank Dorland, an art restorer, examined the Mitchell-Hedges skull in the 1970s and somehow theorized it could be up to 12,000 years old, which, if it were, would completely nix the theory that the Mayans or Aztecs made it. The skull was examined again by the Hewlitt-Packard crystal labs, and then a third time in 2007 by Anna Mitchell-Hedges' surviving husband. Both examinations established what we now know about the skulls: they were manmade, recent, and not magic. Other skulls, including the Smithsonian, Paris, and British Museum skulls have been subject to similar examinations and all concluded to have been made no earlier than 1740.

Even despite all the evidence pointing against it, many documentaries about the secret magic of the skulls. SyFy, Discovery, and the History Channel made the most prevalent and watched of these back in the day. Theories discussed in these docs ranged from connecting the skulls to the 2012 apocalypse to Atlantis to unironic anti-gravity claims. When exactly aliens came into the picture is uncertain, though it's not unreasonable to believe that the extraterrestrial theory only gained attraction after Indiana Jones 4.

Also, Dan Aykroyd has his own vodka brand called Crystal Head, which comes in skull-shaped bottles and draws on the legend of the crystal skulls. There's so much woo there that it deserves its own article debunking it.