Lead ore was first mined in North Wales during Roman times at Pentre Halkyn to be smelted at Flint. The lead that was produced there was stamped with the inscription Deceangli, which was the name of the Celtic tribe occupying the area. In the 17th century an intensive period of Welsh lead mining commenced, bringing a large number of miners from Derbyshire into Wales. There are substantial reserves of the metal in Ceredigion, probably first exploited in the Roman period, and extensively during the revival of metal mining in the reign of Queen Elizabeth I.