The legend of Jason and the Argonauts' heroic quest for the Golden Fleece may provide a fascinating window into real Bronze Age society, say researchers who believe they have found the earliest evidence of a trading gold mine.

The adventure, which was set about 1300 BC — a generation before the Trojan war described by Homer — involves a mission to capture the precious fleece from Colchis, in modern-day Georgia. The mythological fleece has been interpreted in various ways, but is thought by some to symbolize the vast wealth and gold of Georgia.

Although gold was used and traded in ancient times, there has been scant evidence of where the precious metal used in Eurasia during the Bronze Age originated, and whether it was mined or panned from rivers. Gold mines in the Upper Nile region of Egypt and elsewhere in Africa date from 2,500 BC and are believed to have supplied the Ancient Egyptians' needs. But the legend of the Golden Fleece hints at a thriving gold trade in the Caucasus dating back further than was first thought.

In 2004, a team of German and Georgian archaeologists discovered what may be the world's oldest gold mine at Sakdrissi, about 70 kilometres southwest of Tbilisi. Thomas Stöllner and Andreas Hauptmann of Ruhr University in Bochum, Germany, and Irina Gambashidze, an archaeologist from the Centre of Archaeological Studies in Tbilisi, dated the mine to around 3000 BC.

Now, the researchers have produced evidence that suggests this mine was trading as far back as 2500 BC. The team analysed samples of gold from the mine and compared them with gold from some 25 ancient artefacts dating from 2500 to 1500 BC in the Bronze Age. The beautifully worked pieces, housed in museum collections in Georgia and neighbouring countries, include needles, necklaces and rings. The gold was analysed using a process called LA–ICP–MS (laser ablation–inductively coupled plasma–mass spectrometry), in which a tiny layer of surface metal is vaporized and the various elements in the vapour are identified by their mass.

Analysis of Bronze Age artefacts, such as the lion (inset), offers historical links to the Golden Fleece. Credit: THE ART ARCHIVE/CORBIS

The ratio of trace elements in the gold helps to pinpoint where it came from. In this case, the team found similar levels of lead and osmium in the gold from the mine in Sakdrissi as in the artefacts. But the clincher was the unusually high amount of antimony in the artefacts, which is characteristic of the particular geochemistry at Sakdrissi.

Although this suggests a strong link between the mine and the artefacts, it is possible that the gold used was not mined, but panned from rivers in the local area. Villagers in parts of Georgia are still reported to pan the rivers for gold using sheep fleeces — another potential link to the tale of the Golden Fleece. Gold obtained from rivers tends to contain elevated levels of metals such as osmium, tin and palladium, so the archaeologists are now assessing the osmium levels in gold taken from the river to see whether the gold in the artefacts was panned or mined.

Fingerprinting gold is one of the most difficult tasks in archaeometry, says Maria-Filomena Guerra, a physicist at the Centre for Research and Restoration of the Museums of France in Paris, who is separately trying to follow the gold trail. Guerra's team has been analysing gold artefacts from a Mycenaean tomb at Kazanaki near Volos, the modern Greek town close to the area where legend says Jason came from. The tomb dates from 1400 BC and Guerra has so far analysed a gold-beaded necklace and gold leaf interred there, using a technique called PIXE XRF (particle-induced X-ray emission X-ray fluorescence).

Guerra found levels of tin, platinum and palladium in the tomb samples that indicate the gold came from a river source and was almost certainly panned for, she says. She now plans further analyses to prove her hunch that the gold was panned in Georgia.