Nearly 2,000 years after Vesuvius, scientists are studying a black glass-like mass inside a skull: They say it may be vitrified brain tissue

Almost two thousand years after Herculaneum was buried under the shadow of Mount Vesuvius, scientists say that a mysterious black matter found inside a victim's skull may represent one of the most unusual forms of preservation in history.For many years, it was nothing but an artefact - a black glass-like material inside the skull of the person who died from the eruption of Mount Vesuvius in AD 79. Currently, scientists suggest that the matter may represent vitrified human brain tissue, an extremely unusual form of preservation.As mentioned in the study of 2025, published in the Nature Journal, such a finding adds a rare case to how extreme heat and rapid cooling can preserve tissue. Researchers argue that the eruption may not have entirely destroyed the victim's brain tissue.A discovery buried beneath volcanic ashThe remains belong to a young male whose body was unearthed from the Collegium Augustalium structure in the Roman city of Herculaneum, which suffered destruction similar to neighbouring Pompeii due to an eruption of Mount Vesuvius about 2,000 years ago.It was the finding of vitrified or glass-like materials in the victim's brain cavity by researchers that sparked initial interest in the case in 2020. Using various analytical techniques, including protein analysis and microscopy, proteins and fatty acids related to the human brain were identified.As noted in the PLOS ONE paper, the paper describes remarkably preserved neuronal structures, including neurons and axons, preserved at a level rarely seen in archaeological specimens. Brains do get recovered sometimes, albeit in rare cases, in archaeology, but they tend to be fossilised or saponified, which means turned into a soap-like substance. This was clearly not what had happened to the Herculaneum brain specimen.How can a brain become glass?This new study provides the strongest explanation available yet.Experts studied samples extracted from the skull and conducted thermal testing on them. According to their analysis, the material reacted similarly to real glass, not burnt organic matter or volcanic activity. As per the experts, the brain of the individual was likely exposed to high temperatures in excess of 510°C due to a superheated cloud caused by the eruption of the volcano. However, more important was the sudden drop in temperature.Glass is formed when there is a sudden cooling process that prevents the liquid from crystallising. In this case, the brain tissue of the victim seems to have undergone vitrification before it could be destroyed by the heat."This process has never previously been documented for human or animal tissue in nature," the study's authors wrote.This material has been described as organic glass by the researchers. The uniqueness of this finding comes from the fact that naturally occurring organic glass is extremely rare. Evidence from earlier Vesuvius researchIt is nothing new that people in Herculaneum were exposed to very high temperatures.In a landmark paper published in Nature in 2001, it was determined that temperatures of up to 500°C were reached by the first pyroclastic surge, which likely instantly killed most people due to overheating.Subsequent research has strengthened that picture. In 2018, a paper describing the thermal behaviour of pyroclastic density currents at Herculaneum was published. Additionally, another study's authors hypothesised that detached clouds of ash would have produced heat fatal enough to cause serious burns almost immediately upon contact.Researchers also studied the skeletons found at Herculaneum and discovered chemical evidence that body fluids evaporated quickly due to the extremely high temperature.Thus, all these works support the idea that people were exposed to extremely high temperatures.Why archaeologists are paying attentionThe importance of the Herculaneum brain is not limited to the particular victim. For a long time, archaeologists had known about certain conditions conducive to soft tissue preservation: freezing, dehydration, tanning, and saponification, for example. Vitreous transformation was never seen as a method of soft tissue conservation.The discovery suggests there might be another, highly improbable process at work in unique circumstances. There remain some doubts as to whether everything is clear regarding this matter. Nevertheless, the authors describe it as a process not previously documented for human or animal tissue in nature.It is the irony inherent in this case that makes it so exceptional. The natural disaster that caused the death of the victim resulted in preserving some of his nervous system tissue in a previously unknown way. Natural catastrophes usually eliminate any traces of their victims. At Herculaneum, a catastrophic volcanic eruption turned out to create a unique archaeological record of tissue preservation.Nearly two millennia later, a fragment of black glass inside a Roman skull is still revealing how how some victims of Herculaneum died and were preserved.