TRICHY: The discovery of an over 2,500-year-old foundry unit made on rock in Pudukottai district throws light on the expertise of people in the Sangam era in extracting metal from its ore while heating it at high temperatures. A team of epigraphists found the foundry near a forest area at Porpanaikottai While ancient foundries made of soil and bricks have been discovered in some parts of the state, this is the first time furnaces carved out on rock have been found, said A Manikandan , a science teacher in a government school and archaeology enthusiast who was part of the team that stumbled upon the relic.Most of the furnaces in circular and oval shape have an average depth of 2.5 feet. Manikandan said that if these furnaces were compared with ancient furnaces found in other parts of the state it can be found that circular furnaces were used to heat up the iron ore which was later transferred to the oval furnaces to extract metal. The foundry could have been built there as iron aluminum silicate is found in abundance in the region.Manikandan said a stone inscription found in the nearby Porpanaikottai fort has been found to belong to the 5th century BC. Going by the structure of the foundry, it is most likely to belong to the Bronze Age.He said the state archaeology department should undertake further explorations at the site. Such sites highlight the ancient culture and heritage of this region and all measures must be taken to preserve it.