Stargazer.
Made from Pietersite.
Used by the ancients to monitor movements of the planets and stars. Believed to have been used in the design and positioning of the ancient monuments such as Stone Henge and the Egyptian Pyramids.
Since it was only possible to track the movements of the planets and stars over many 1000's of years, it was necessary to store this information in a receptacle that could survive for those 1000's of years and be easily retrieved.
Stargazer was such a receptacle.
We, as a global society, have lost the ability to retrieve this information. When we, as a global society, become sufficiently evolved to use this information wisely and for the good of all and to the harm of none, then we will remember the keys of how to access this information.
Until that time, the skulls will appear to many as just elegant and beautiful ornaments. Nothing more.