About 2,000 years ago, a catastrophic event occurred when Mount Vesuvius erupted, engulfing the nearby Roman towns of Herculaneum and Pompeii in a scorching cloud of ash, dust, and volcanic material. The heat was so intense that it transformed one resident’s brain into glass, according to a team of researchers.

The individual’s brain, once a soft and pinkish-white organ, was converted into a hard, sparkly black glass-like material. Furthermore, the glassy remains exhibit preservation at a microscopic level, with the Roman’s axons and neurons remarkably preserved due to the extreme conditions of the volcanic eruption. The team’s findings were published in Scientific Reports today.

According to the researchers, “Our thorough chemical and physical analysis of the material sampled from the skull of a human body buried at Herculaneum by the 79 CE eruption of Mount Vesuvius provides compelling evidence that these are human brain remains, composed of organic glass formed at high temperatures, a process of preservation never previously documented for human or animal tissue, neither brain nor any other kind.”

The individual’s remains were discovered in a bed at the Collegium Augustalium in Herculaneum. The deceased was a young male, approximately 20 years old, and is believed to be the guardian of the collegium, dedicated to the worship of Emperor Augustus, who had passed away 65 years prior to the eruption.

Although human brain preservation is rare in archaeological records, it has been documented through various methods such as dehydration, saponification, tanning, and freezing. However, vitrification, or the conversion of a material into a glass-like substance, of a human brain is unprecedented due to the specific high temperatures and rapid cooling required.

The remarkable preservation of the individual’s brain was initially described in 2020, but at the time, researchers were unable to understand the mechanism behind the vitrification. Now, they have a deeper understanding of the extreme and unique conditions that led to the formation of the glass brain.

The researchers noted in their paper that the temperatures of the pyroclastic flows that buried Pompeii and Herculaneum were several hundred degrees, which would typically be sufficient to destroy soft tissue.

The individual’s glassy remains were “formed by a unique process of vitrification of his brain at very high temperature, and is the only such occurrence on Earth,” according to the researchers. “Calorimetric analyses show that the temperature at which the brain transformed into glass was well above 510 °C [950 degrees Fahrenheit], implying that the body was exposed to the passage and vanishing of a short-lived, dilute and much hotter pyroclastic flow, explaining its early fast heating and the following very fast cooling.”

The team added that this unique process resulted in the perfect preservation of the brain and its microstructures. Indeed, analysis of the glass using a scanning electron microscope revealed neurons, axons, and other neural structures, bearing a striking resemblance to the processes used to reveal writing on scrolls carbonized by the eruption of Vesuvius, also found in a Herculaneum villa.

The researchers also propose that the brain was in a unique position to be preserved, as the individual’s skull and spine protected the organ from the brunt of the intense pyroclastic flow. Although extremely hot and fatal, the initial wave of heat from Vesuvius’ eruption was not the kind of messy deluge of lava typically associated with volcanic eruptions.

If you want to express a strong threat, you might consider replacing “your ass is grass” with “your brain is glass.”