A unique, dark-colored glass found inside the skull of a Roman killed by the eruption of Mount Vesuvius is his brain—cooked into a fossil by an ash cloud.
This is the horrific revelation of an international team of researchers who analyzed the glass to determine what conditions would have been needed to produce it.
Archaeologists first unearthed the remains of the poor young man—estimated to be in his twenties—in 1960; the black glass was discovered in his skull in 2020.
He appeared to have died lying down in his bed in the “Collegium Augustalium”—a building owned by an imperial cult that worshipped the former emperor Augustus—in Herculaneum.
Like its more famous neighbor, Pompeii, this ancient Roman town was destroyed when Vesuvius erupted in the year 79 AD.
Whereas in Pompeii the streets were buried under more than a dozen feet of volcanic ash and pumice, Herculaneum was hit by blazing ‘pyroclastic’ flows of gas and debris.
However, the findings of the new study suggest that the pyroclastic flows were not the first deadly phenomena that Vesuvius threw at Herculaneum—but such were instead preceded by a super-heated and short-lived ash cloud.
Only this, the researchers say, could have provided the extreme temperatures (in excess of 950 degrees Fahrenheit) and subsequent rapid cooling to create the glass brain fossil.
(This is why glass rarely forms in nature, as it requires liquid material to cool fast enough that it doesn’t develop a crystalline structure—calling for a significant temperature difference with the surrounding environment.)
In contrast, the subsequent pyroclastic flows would have only reached 869 degrees Fahrenheit—and would have cooled down too slowly.
“Only later in the night was the city completely buried by the deposits of the pyroclastic flows,” said paper author and volcanologist professor Guido Giordano of the Roma Tre University in a statement.
“This scenario is of great importance not only for historical and volcanological reconstruction, but also for civil protection purposes.
“It defines a very high danger even for very diluted flows that do not have great impacts on the structures but that can be lethal due to their temperatures, the knowledge of which can translate into effective prevention and mitigation measures.”
“A cerebral and spinal material like this, vitrified, not only has never been found in any other of the hundreds of skeletons of victims of the Vesuvian eruption of 79 AD, but it is the only example of its kind known in the world,” added paper author PierPaolo Petrone of the University of Naples Federico II in a statement.
“It is likely that the particular conditions that occurred at the beginning of the eruption at the place of discovery, as well as the protection of the skull bones and the spinal column of the individual, created the conditions for the brain and bone marrow to survive the thermal impact, subsequently allowing this unique organic glass to form.”
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Reference
Giordano, G., Pensa, A., Vona, A., Di Genova, D., Al-Mukadam, R., Romano, C., Deubener, J., Frontoni, A., & Petrone, P. (2025). Unique formation of organic glass from a human brain in the Vesuvius eruption of 79 CE. Scientific Reports. https://doi.org/10.1038/s41598-025-88894-5
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