This example is in the British Museum.
Crystal human skulls with alleged mystical powers began turning up in Central America in the late 19th and early 20th centuries. They were thought to be artifacts from Aztec and Mayan cultures. A number of museums and wealthy individual collectors wanted to get their hands on them.
Where Did the Skulls Come from?
Some of the skulls were life-sized, while others were miniatures; all elicited excitement from the archaeological community. Some suggested they came from cultures that moved into Central America from the lost city of Atlantis. There was a body of opinion that said they were left behind by aliens who had visited Earth long before recorded history.