Boy’s body was mummified and turned green by a copper coffin

A teenage boy buried nearly three centuries ago in a copper box in northern Italy has become the only nearly complete green mummy ever known.

Other ancient body parts were partially mummified or turned green after being buried with copper or bronze objects, e.g. green mummified hand of a newborn baby clutching a copper coinburied in a ceramic pot in medieval Hungary.

However, the Italian mummy is intact except for the legs. With the exception of his left leg, he is almost entirely green from skin to bone.

The mummy was discovered in the basement of an ancient villa in Bologna in 1987 and sent for forensic examination to the University of Bologna. Forensic experts determined that the body was a 12-14 year old boy. Since then it has been carefully kept at the university.

Alabiso AlabisoA conservationist at the University of Rome, Tor Vergata, contributed to the study of the mummy by a wide range of specialists, including geneticists, anthropologists, radiologists, mathematicians, physicists and computer scientists. “It was a wonderful interdisciplinary collaboration,” she says.

The researchers conducted several in-depth chemical and physical analyzes of the mummy. Carbon dating has determined that the boy's death occurred between 1617 and 1814, Alabiso says, and there are no obvious signs of injury or illness on the mummy.

Copper helped preserve hard and soft tissue—as expected given its known antimicrobial properties, Alabiso says. But it also reacted with acids that flowed from the body and corroded the box. This led to the formation of copper corrosion products that interacted with chemical compounds in the bone. Gradually, copper ions replaced calcium in the boy's skeleton, strengthening the bone structure for a long time and coloring the affected areas various shades of green.

As for the skin, it was covered with a crust of copper corrosion products called patina, a pale green coating that forms on copper and bronze statues. According to Alabiso, the patina formed when the copper reacted with water and carbon dioxide as the body broke down.

“This completely changes our view of the role of heavy metals, because their impact on preservation is more complex than we might expect,” she says.

The bottom of the box eventually cracked – possibly due to acid – allowing the liquid to spill out, leaving the body in a cool, dry chamber with little oxygen, which slowed decomposition. The boy's legs could have come off and gotten lost at that time, Alabiso said.

“It was a very emotional experience for me to work with these unique human remains,” she says.

Julia Gallo At the Collège de France in Paris I recently saw images of a mummy for the first time – and was delighted. “Wow, this is incredible!” she says. “This is so beautiful! This whole example is quite fascinating.”

Gallo says the researchers have done an excellent job of understanding all the physical and chemical processes that lead to mummification and body color changes. “The evidence strongly supports their arguments regarding the preservation and coloration of tissues and bones.”

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