- Japanese: 鉄 (tetsu / kurogane)
In the Yamato period, the Wakabe clan maintained a monopoly on iron ore for a time; this came to an end in or around the reign of Emperor Kôtoku (645-654), after which all iron ore had to be turned over to the Imperial Court.
In the Edo period, the shogunate established a za guild in 1780, at the direction of Tanuma Okitsugu, which would have a monopoly on the sale and distribution of iron. Its offices were attached to those of the Osaka ginza (Silver Monopoly), which then collected all iron pig mined in the archipelago, to be resold out into the realm. Established alongside a similar brass monopoly, both were quite short-lived, being abolished in 1787 by Matsudaira Sadanobu.