The technique of iron smelting appears to have come to the Central Plain from Xinjiang, and it is something of a mystery how the technique came to Xinjiang. Perhaps it came from the Chust culture in Ferghana, but the possibility of independent invention cannot be entirely dismissed. In the Central Plain the first smelted iron was used as a substitute for meteoritic iron in prestige weapons, but the Iron Age began with the invention of cast iron, perhaps in the 6th century BCE.