According to an Athonite tradition and belief, the skulls of monks can reveal certain things about their lives. We see this when we take a tour of the Ossuary in the Monastery of Saint Dionysios of Olympus.
For example, if a skull has a darkened color, it could indicate that the monk lived either a sinful or heretical life, but if it is golden-yellowish then it could indicate that the monk was virtuous and holy. Another strong indicator of holiness is if a skull exudes a myrrh-like substance that is fragrant.
It is also believed that hieromonks (monks who have been ordained as priests) have something the skulls of regular monks don't have: on top of the cranium there is a form of the sign of the cross dividing it in four.
All these signs can be seen in various skulls of the approximately 1,400 skulls in the Ossuary in the Monastery of Saint Dionysios, except a darkened skull.