Iron From Space Helps Settle Age Of One Of Spain's Greatest Treasures

One of the most important and enigmatic Bronze Age discoveries appears to have incorporated meteoritic iron. The discovery could resolve confusion about the ages not only of the iron items, but the hoard of gold with which they were buried.

The Treasure of Villena was discovered in what is now eastern Spain in 1963. The 59 bracelets, bowls, and assorted items are most famous for their wealth of gold, but the more intriguing aspect is the iron from which two of the items were made. These were the oldest iron pieces found on the Iberian Peninsula, and based on the accompanying riches appeared to date to at least 3,000 years ago. The origin of the entire Treasure is mysterious enough, given the lack of evidence of the civilization that made them, and the presence of apparently Bronze Age items with the iron pieces deepened the mystery. 

However, long before humanity learned to mine and smelt iron, we were using iron from meteorites found on the Earth’s surface. Most famously, Tutankhamun had a dagger forged from meteoritic iron, its possession by the boy pharaoh demonstrating the immense value placed on such items. The capacity to work the mix of iron, nickel, and sometimes cobalt known as meteoritic iron must have developed independently in many places, since pre-Iron Age examples are found in North America, southern Africa, and Tibet, as well as the Middle East.

One iron piece is a hollow hemisphere partially covered in gold (referred to as a cap or pommel) and the other a bracelet. Their purpose is unknown, but at face value their existence indicates the treasure must date from the Iron Age, albeit the very start when ironwork was new enough to be very valuable. Yet if so, what are they doing with so much gold in the Bronze Age style? 

However, if the iron from which the two pieces are made is from the heavens, not the Earth, there would be no discrepancy.

Inevitably archaeologists have been keen to test the iron pieces for a long time. However, the combination of corrosion making most ancient iron very delicate, and the desire to protect the items from damaging test methods, has been an obstruction. Increasing availability of non-destructive tests has changed the situation, leading retired museum curator Salvador Rovira-Llorens and co-authors to explore the pieces' composition.

Portable X-ray fluorescence spectrometry produced uncertain results, so the team turned to mass spectrometry applied to tiny samples. They found the proportion of nickel in the cap (5.5 percent) is very much in line with known iron meteorites, and well above what is usually found in terrestrial deposits. On the other hand, preliminary measurements of the bracelet gave the distinctly ambiguous result of 2.8 percent.

Corrosion can cause more nickel to leach than iron, however, lowering its concentration. Deeper analysis revealed more nickel towards in interior areas less exposed to air and water, indicating the bracelet was made from meteoritic iron as well. Indeed, it is likely it was from the same meteorite, with the uncorroded composition being the same. Matching the composition to a specific meteorite has not so far been possible, however.

“The available data suggest that the cap and bracelet from the Treasure of Villena would currently be the first two pieces attributable to meteoritic iron in the Iberian Peninsula, which is compatible with a Late Bronze chronology, prior to the beginning of the widespread production of terrestrial iron,” the authors write.

Outside Greenland, almost all terrestrial iron is in the form of iron oxide, which Bronze Age people lacked the technology to reduce. Meteorites not only avoided the need for this, but the iron nickel alloys were more resistant to corrosion even once pure iron became available. The immensely rare product was the Earthly equivalent of Valyrian steel in Westeros, given immense value by its extreme rarity.

The study is published in Trabajos de Prehistoria.