Forty years ago, in 1987, inside the basement of a villa in Bologna, a copper funerary cist was discovered, containing partially mummified human remains, green in colour. The particular color of the body is due to the copper that contained it: the copper ions, produced by the corrosion of the metal, interacted with bones and tissues, and the humid and oxygen-poor environment favored saponification and slowed down decomposition. The remains, analyzed by the Institute of Forensic Medicine of the University of Bologna, turned out to belong to a young male individual (who probably died between 12 and 14 years of age), in a fetal position. The radiocarbon method dated the mummy to a period between 1617 and 1814. What surprised the researchers, however, was the coloring of the mummy: except for the right leg, the mummified bones and soft tissues are in fact green.
To understand why the remains of the young man took on this particular color, some samples of bones and soft tissues were analyzed by a research group from the Tor Vergata University of Rome, coordinated by Dr. Annamaria Alabiso. The scholars took 7 samples, 4 of which were bone (the twelfth rib, a phalanx, a scapula and the fibula of the leg not colored green) and 3 from mummified soft tissues (two from the chest and one from the left leg).
The samples were subjected to infrared spectroscopy, Raman spectroscopy and scanning electron microscope analysis. The data obtained from these analyzes allowed the Tor Vergata researchers to understand how the boy’s remains managed to be preserved so well and above all why they took on this particular green colour.
A strong concentration of pseudomalachite (product of copper oxidation) was noted in the green-stained bones, which replaced the calcium. Collagen proteins were highly degraded, both in bone and skin samples. On the latter, the presence of malachite (another product of copper oxidation) and adipocere was recorded, a substance produced in the saponification process of a corpse, when the decomposition processes take place in a humid but oxygen-free environment. Substances produced by the oxidation of copper caused the bones and soft tissues to turn green.
The remains of the young man from Bologna underwent more unique than rare decomposition processes, a sort of “natural chemical mummification”. The body, after being inserted inside the copper funerary cist, began to putrefy. The normal decomposition process was slowed down both by the low temperature of the underground, by the low presence of oxygen inside the cist, and by the fact that this, undergoing a rupture at the bottom (which probably caused the loss of the remains of the feet, which were absent), allowed the cadaveric fluids to gradually flow out. The latter, in contact with the copper of the cyst, caused corrosion, with the release of copper ions which interacted with the bones and soft tissues. These severely affected the collagen proteins, but thanks to the biocidal properties of copper they also further slowed down the putrefaction process. In short, the “green mummy” of Bologna is the particular result of a combination of environmental factors: low temperatures, low oxygen levels, and the biocidal action of copper ions.
