A detailed analysis of the skull’s surface revealed minute rotary scratch marks around the eye sockets, teeth and cranium. This was clear evidence that the skull was cut and polished with a wheeled instrument – and the Aztecs never used the wheel. The researchers concluded that the skulls were cut from a piece of Brazilian rock crystal in Europe. They were then probably sold to collectors as a relic from the ancient Aztec civilization. Many museums now have removed the skulls from display because of their questionable origins. (via 10 Recent Scientifically Solved Mysteries)