Mount Vesuvius, a famous volcano in Italy, blew up in 79 AD with such force that it engulfed the cities of Pompeii and Herculaneum under volcanic ash. Thousands perished, and the cities were concealed for almost 1,700 years before they were excavated in the 18th century.

But what was even more astonishing about this story is what was done to one specific man. When scientists examined his remains, they discovered something that had never been seen before—his brain had been replaced with glass!

How can a brain turn into glass?

Typically, when a person is subjected to fire or intense heat, the flesh is consumed. However, in this particular instance, something extremely unusual occurred—his brain solidified. This is to say that it changed into a glass-like state.

As forensic anthropologist Pier Paolo Petrone explains, this was because a searing hot cloud of ash—temperatures of at least 510°C (950°F)—suddenly engulfed the city, instantly killing all. The heat was so intense that it vaporized the brain's organic matter, and then cooled so rapidly that it turned into glass.

The man, who was thought to be in charge of the College of the Augustales, was discovered resting on his bed when the eruption happened. His body was initially discovered during the 1960s, but in 2018, when researchers re-studied his skull, they noticed something that made them curious.

"I was in the room where the college's custodian was lying in his bed to document his charred bones. Under the lamp, I suddenly saw small glassy remains glittering in the volcanic ash that filled the skull," said Petrone, as quoted by Reuters.

When scientists got a closer inspection, they noticed small, reflective black shards resembling obsidian, a volcanic glass that occurs naturally. However, unlike obsidian, these were brittle and readily crumbled.

Scientists had never seen human brain tissue vitrified in this way before. Although some rare instances of wood vitrification had been found in Pompeii and Herculaneum, no animal or human remains had been so vitrified. 

Additional testing verified that these glassy fragments were made up of proteins and fatty acids—essential parts of human brain tissue. The central nervous system, such as nerve cells and axons, was also preserved in an extremely good condition.

The discovery provides scientists with new perspectives on how dangerous heat can behave on the human body. The discovery also indicates what occurred with the fatal explosion of Vesuvius.

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