A fragment of organic glass found in the skull of the deceased Herculaneum. Credit: Pier Paolo Petrone
79 CE Mount Unique dark-colored organic glass inside the skull of an individual who died in Herculaneum in the eruption of Bethbius. The conclusions from studies published in the science report are based on an analysis of the physical properties of glass, which are thought to make up an individual’s fossilized brain.
Glass rarely occurs naturally due to the specific conditions required for formation. For a material to become glass, it must be cooled quickly enough to crystallize when its liquid form becomes solid. It requires a large temperature difference between the material and its surroundings. The material must then be solid at a temperature well above the ambient temperature.
As a result, organic glass is extremely difficult to form, as the ambient temperature is rarely low enough for water (an important component of organic matter) to solidify. In 2020, the only natural organic glass was identified in Italian Herculanem, but it was not clear how this glass was formed.
Guido Giordano and colleagues analyzed fragments of glass sampled from the skull and spinal cord of the deceased Herculaneum. The results of analysis, including imaging using x-rays and electron microscopes, show that in order for the brain to become glass, it must be heated to at least 510 degrees Celsius before rapidly cooling.
Organic glass samples under direct light. This is the section in Figure 2 of the published article. Credit: Guido Giordano et al./Scientific Reports
The ruins of the deceased in the bed of the Collegium Augustrium at Herculaneum. Credit: Pier Paolo Petrone
Annotated images of the deceased ruins in a bed at Collegium Augustalium in Herculaneum. This is the section in Figure 1 of the published article. Credit: Guido Giordano et al./Scientific Reports
The authors note that because the temperature of these streams did not exceed 465°C and were slowly cooled, this could not occur if individuals were heated by the pyroclastic streams that buried Herculaneum.
Therefore, the authors conclude that, based on modern observations of volcanic eruptions, an ultra-hot ash cloud ran out, rapidly dissipating as the first fatal event during the Vesuvius eruption. They theorize that such events rapidly cool to ambient temperatures as the clouds dissipate after increasing the temperature of individuals above 510 degrees Celsius. The bones of the individual’s skull and spinal bones protected the brain from complete thermal collapse, allowing this unique organic glass to form.
Details: Guido Giordano, Unique Formation of Organic Glass from the Human Brain during the Vesuvius Eruption in 79 AD, Science Report (2025). doi: 10.1038/s41598-025-88894-5. www.nature.com/articles/S41598-025-88894-5
Quote: Vesuvian Ashcloud Suspected Turning Brain into Glass (March 2, 2025) Retrieved from March 2, 2025 from https://phys.org/news/2025-02-vesubian-ash-cloud-brain-glass.html
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