Pig iron
Smelting and producing wrought iron was known in ancient Europe and the Middle East, but it was produced in bloomeries by direct reduction. Pig iron was not produced in Europe before the Middle Ages. The Chinese were making pig iron by the later Zhou dynasty (which ended in 256 BC). Furnaces such as Lapphyttan in Sweden may date back to the 12th century; and some in Mark (today part of Westphalia, Germany) to the 13th. It remains to be established whether these northern European developments derive from Chinese ones. Wagner has postulated a possible link via Persian contacts with China along the Silk Road and Viking contacts with Persia, but there is a chronological gap between the Viking period and Lapphyttan.