A guy was casually diving around when he found a very unexpected treasure near the Arzachena shore in Sardinia, Italy: Tens of thousands of coins from the 4th century under the sand, in between the Posidonia oceanica of the Mediterranean Sea. There’s around 30,000 to 50,000 coins, and they’re mostly follis, which became popular after the Diocletian reforms in the Roman Empire.
They told the authorities and the Italian Ministry of Culture about it, and the general director of archeology, Luigi La Rocca, explained the importance of it by affirming, “The treasure found in the waters off Arzachena represents one of the most important coin discoveries.”
But this was not it; along with the coins, fragments of the Roman amphorae showed up too, which is a clue that merchant ships from the Roman era were passing by that area. The magnitude of this finding was compared to the Seaton Down Hoard of Devon in the United Kingdom, where they collected about 22,888 coins in 2013.
This kind of discovery can say a lot about underwater archeology and numismatics, but they also say a lot about routes, markets, and political decisions that were happening above water 1,600 years ago.
A treasure under Sardinia’s waters
The findings extended into a shallow zone in front of Arzachena, where the currents usually move objects without burying them immediately. The team mapped two main “stains” of coins in the sand, and they were surrounded by dense prairies of Posidonia oceanica. A marine plant that was key for this whole observation because their roots make sediments, they create zones with little oxygen, and their leaves calm down the waves.
The bottom of the ocean here works as a natural folder; it can keep metal and ceramic in good shape for centuries. The Roman amphorae (large ceramic jars) fragments from different workshops of the Roman world say that this was probably a commercial route, where products from different places were traveling together.
If Sardinia confirms 50,000 or more coins, it will become the reference point for the study of late-Roman money in the western Mediterranean.
What the coins tell
The pieces seem to be mostly Follis. These are big bronze coins that, in the beginning, would be covered by a light silver layer to “dress” the metal base. But with time, both the weight and the silver were lighter. This tells a story about the politics of the Roman Empire, which had to finance armies, administration, construction work, and more. And even though the coin changed, the daily exchange continued. A sailor could pay for their food with the same type of coin that a farmer would inland.
Finding treasure like this allows the historians to understand that money travelled in and outland.
The study starts with a soft clean process, they stabilize it and catalog it, piece by piece, so they don’t erase any important information. Then, numismatics comes in to identify emperors, lemmas, dates, and “mints” (workshops). If there’s more of a certain “mints” that could show some routes on the Mediterranean Sea and the Tyrrhenian Sea.
At the same time, the underwater archaeology is in charge of studying the physical context, meaning a storm that provoked part of that load to overturn, a container that broke, or maybe the crew payments saved for the new port.
The conclusion for now is that a container opened up and the currents “brushed” it until they extended at the bottom of the sea.
As Luigi La Rocca said, this is one of the most revealing discoveries in the last years. This is why taking care of our oceans and prairies is so important; it’s not just protecting nature, it’s also preserving the history of the past, our past.