Crystal skulls are not uncommon or terribly mysterious. Thousands are produced every year in Brazil, China, and Germany. But there are a handful of these rather macabre objects that have fueled intense interest and controversy among archaeologists, scientists, spiritualists, and museum officials for more than a century.

There are perhaps a dozen of these rare crystal skulls in private and public collections. Some are crystal clear, others of smoky or colored quartz. Some are actual human size and of very fine detail, while others are smaller and less refined. All are believed to originate from Mexico and Central America.

Many believe these skulls were carved thousands or even tens of thousands of years ago by an ancient Mesoamerican civilization. Others