Glass brain shard from man who died in Mount Vesuvius eruption. (Credit: Giordano, et al / Nature)
In a nutshell
- Scientists discovered a human brain from 79 CE Vesuvius eruption transformed into glass—the only known case of natural organic glass preservation in history.
- The brain vitrified at temperatures above 510°C followed by extremely rapid cooling, revealing a new timeline of volcanic hazards during the disaster.
- This unique preservation was only possible because of a perfect sequence: superheated ash cloud exposure, rapid cooling as the cloud dissipated, then burial by cooler volcanic flows.
Never-before-seen phenomenon shows how volcanic ash flash-froze victim’s mind
ROME — When volcanic disaster struck the Roman city of Herculaneum in 79 CE, a young man, believed to have been a guardian of a public building, met his demise in a flash of superheated ash. But his brain underwent a transformation so rare that scientists had previously considered it impossible in nature: it turned to glass.
Led by scientists from Università Roma Tre, the study documents the first and only case of human organic tissue naturally vitrifying into a glass-like state. It’s certainly an exciting new addition to the chronicles of ancient Roman history and scientific understanding.
How Glass Forms: A Rare Natural Phenomenon
Glass forms when a liquid cools so rapidly that its molecules don’t have time to arrange themselves into crystals. Instead, they become locked in a disordered state, creating what scientists call a glass transition. While this process is common with certain materials like silicates (the stuff of volcanic obsidian), organic tissues like brains are primarily composed of water. This means they typically can only be preserved as glass through rapid cooling to temperatures well below freezing. Such preservation methods are reversible; when the temperature rises again, the tissue returns to its original soft state.
This natural law of physics makes the Herculaneum find particularly perplexing. How could a brain possibly vitrify in the midst of a volcanic eruption that reached temperatures of several hundred degrees Celsius?
The Guardian of Herculaneum: An Unprecedented Discovery
The victim, believed to be approximately 20 years old, was discovered in the Collegium Augustalium, a public building dedicated to the worship of Emperor Augustus. He is believed to have been the guardian of this important structure, which was located on Herculaneum’s main street. When archaeologists examined his remains, they discovered the unique dark-colored organic glass with the appearance of obsidian.
Through detailed analysis including microscopy, heat testing, and light-based identification techniques, researchers determined this wasn’t just any preserved organic material. It was actually the victim’s brain transformed into glass at temperatures exceeding 510°C. More astonishing still, previous research in 2020 confirmed the presence of preserved neurons in the vitrified material, adding to the significance of this latest discovery.
Of the approximately 2,000 bodies unearthed throughout archaeological sites around Vesuvius, this is the only instance of vitrified brain tissue ever discovered. This uniqueness suggests that highly specific conditions must have been met for such preservation to occur.
How Scientists Solved the Mystery
To determine exactly how this preservation happened, researchers conducted experiments using heat testing at different rates. By heating fragments of the preserved brain at both slow (25 degrees Celsius per minute) and fast (1000 degrees Celsius per second) rates, they identified the temperature at which the brain would have transformed from tissue to glass.
Their findings, revealed that the brain likely underwent vitrification at around 510°C, with 420°C representing the lower boundary observed in experiments. This analysis provided a critical clue: the vitrification must have occurred through an extremely rapid cooling process after exposure to intense heat.
Rewriting Vesuvius’s Deadly Timeline
In Scientific Reports, the researchers propose a revised understanding of how Vesuvius claimed its victims. Rather than the common assumption that volcanic flows killed and buried victims simultaneously, the evidence suggests a more complex sequence.
According to the researchers, the bones of the individual’s skull and spine likely protected the brain from complete thermal breakdown, allowing fragments to form this unique organic glass.
A super-heated ash cloud which dissipated quickly was the first deadly event during the eruption of Vesuvius. This initial surge exposed the guardian to temperatures well above 510°C but didn’t destroy his brain completely, possibly because the skull provided some protection.
As this ash cloud rapidly dissipated, temperatures returned just as quickly, causing the brain tissue to turn into glass. Only later did the thicker, slightly cooler volcanic flows bury the body and the city, preserving this unique phenomenon until its discovery nearly two millennia later.
The authors emphasize that this vitrification process couldn’t have occurred if the individual was heated solely by the volcanic flows which buried Herculaneum, as the temperatures of these flows did not reach higher than 465 degrees Celsius and would have cooled slowly.
Perfect Storm of Conditions: Why This Find Is Unique
The unique preservation conditions explain why this remains the only example of its kind. The brain tissue had to be exposed to extreme temperatures, but rapid cooling allowed partial preservation through vitrification. Then it needed to cool at an extraordinarily rapid rate—something that would only be possible during a very specific type of volcanic event. Finally, the subsequent burial had to occur at temperatures lower than the glass transition temperature to prevent the material from reverting to a soft state and decomposing.
The material was first identified as potentially vitrified brain tissue in 2020, but the exact mechanism of how this glass formed remained unclear until this latest research. Through comprehensive analysis of the physical properties of the glass, the research team has now provided a convincing explanation for this unprecedented preservation phenomenon.
A Window Into Ancient Catastrophe
For volcano experts, the remarkable discovery provides evidence of a specific type of hazard—extremely hot but short-lived ash clouds that can precede the main volcanic flows. For archaeologists and forensic scientists, it demonstrates an unprecedented preservation mechanism.
The guardian of the Collegium Augustalium, whose name is lost to history, has provided modern science with an extraordinary window into both the human brain and the catastrophic events of 79 CE. Through the perfect storm of conditions that claimed his life, his mind has been preserved in a way previously thought impossible—a glass-like testament to both the destructive and preservative powers of nature.
Paper Summary
Methodology
The researchers used several techniques to study the brain glass. They took detailed images using powerful electron microscopes, which showed typical glass features including shell-like fractures with sharp angles. They measured the material’s density and internal structure, finding it had very little porosity (just 1.4% tiny bubbles). Chemical analysis showed the material was mostly carbon and oxygen with small amounts of other elements like sodium and potassium.
To understand how the material would behave when heated, they used a technique that measures heat absorption and release during physical changes. This helped them identify key temperature points where the glass would transition between states. They also used a method that examines how light interacts with the material’s molecules to confirm its organic nature and track structural changes after heating.
Results
The analysis confirmed several key points. The material’s physical properties matched those of glass. Chemical testing showed it was primarily carbon-based, supporting its origin as brain tissue. Heat testing revealed critical temperature thresholds: at slower heating rates, the material began to change at 420°C, while at faster rates, this happened at 510°C.
When heated above these temperatures, the material showed signs of releasing gas (around 500°C) followed by crystallization (at 530-600°C). After these changes, additional heating and cooling showed no further thermal events, indicating the material was no longer glass-like. Light-based analysis confirmed the carbon nature of the material and showed that heating caused increasing structural organization – exactly what would be expected as a glassy material transforms under heat.
Limitations
Despite the comprehensive analysis, some limitations exist in this research. The primary challenge was the inability to determine the exact cooling rate experienced by the brain during the volcanic event. Normally, this would require knowledge of the temperature dependence of the material’s viscosity, which doesn’t exist for this unique substance. Additionally, the study was constrained by the limited sample size – this is the only known example of vitrified brain tissue from the eruption, making comparative analysis impossible.
The researchers also acknowledged that while they could determine the approximate temperature range for the glass transition, precise values remain uncertain due to experimental limitations and the ancient nature of the samples. Furthermore, the exact mechanism of preservation for neural structures within the vitrified material could not be fully explained. Finally, the study could not definitively determine how much of the original brain structure remained intact before vitrification, as the material was found in fragments rather than as a complete preserved organ.
Funding Information
The research received funding from several sources, including grants from the Department of Science at Università Roma Tre through the MIUR-Italy Dipartimenti di Eccellenza program. Additional funding came from the European Research Council under the European Union’s Horizon Europe research and innovation program (NANOVOLC project), the Deutsche Forschungsgemeinschaft, and the European Union’s Next Generation EU initiative. The authors declared no competing interests in relation to the research.
Publication Details
This research paper titled “Unique formation of organic glass from a human brain in the Vesuvius eruption of 79 CE” was published in Scientific Reports (volume 15, article number 5955) on February 27, 2025. The study was conducted by an international team led by Guido Giordano from Università Roma Tre in Italy, with contributors from several Italian and German research institutions. The paper is available under an open access license.
