The world's oldest mint, dating back about 2,500 years, has been uncovered in Central China's Henan province.

Using radiocarbon dating, Chinese archaeologists have confirmed that a bronze casting workshop at the ruins of Guanzhuang in Xingyang city, the western part of the Henan provincial capital of Zhengzhou, began minting standardized metal money around 640-550 BC, making it the earliest known workshop of its kind in the world.

During further excavation, four items related to coin manufacture were unearthed at the site, including finished coins, used and unused coin molds, as well as outer molds, says Han Guohe, an archaeology professor from Zhengzhou University.

Archaeologists have also uncovered several pits where a large quantity of bronze casting waste was dumped, with two finished metal coins found in one of the pits.

The coins are believed to be the currency that was in circulation during the Spring and Autumn (770-476 BC) and Warring States (475-221 BC) periods, and are among ancient China's earliest coins, according to Gao Xiangping, the archaeological team leader of the excavation at the Guanzhuang ruins.

New discoveries at the workshop site not only provide a clear archaeological background for studies on the exact time of currency production, but also help reflect the social and economic mechanism during the development of metal money, Han adds.

The Guanzhuang ruins, first excavated in 2010, is a complete city site, built about 800 BC during the Western Zhou Dynasty (c.11th century-771 BC) and abandoned about 450 BC. A large area made up of handicraft workshops was found at the site, where bronze casting, pottery and bone artifact production had been carried out.

A paper on the coin workshop has been published by Antiquity, a peer-reviewed archaeological journal.