LEGEND OF THE CRYSTAL BRAIN

When most people envision the victims of the eruption of Mount Vesuvius in A.D. 79 that destroyed the cities of Pompeii and Herculaneum, they think of the casts of their bodies made by pouring plaster into voids left by their decaying corpses. Yet not all the physical remains of those who perished in the cataclysm decayed. In one case, a remarkable transformation occurred—a man’s brain turned to glass.

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Human tissue is composed largely of water. Thus, explains forensic anthropologist Pier Paolo Petrone of the University of Naples Federico II, when exposed to intense heat, it vaporizes. Exposure to the extreme heat of a volcanic eruption should completely destroy the soft tissue of any living organism in its path. At sites across the world, a relatively small number of human brains have been preserved through saponification, a natural process by which human tissue transforms into triglycerides that are then converted to glycerol and fatty acids, or soap. On rare occasions, human brains have been preserved by dehydration, tanning, or freezing. But, says volcanologist Guido Giordano of Roma Tre University, this is the only example of a vitrified brain—or, indeed, vitrified tissue of any sort—in the archaeological record. Scientists long believed that the only way tissue could become vitrified was by exposure to very low temperatures, or cryopreservation. This was clearly not what occurred during the scorching eruption.