Copper

• Japanese: 赤金・銅 (akagane, dou)

Copper has been used for coinage in China and Japan since ancient times, and was a major maritime trade and tribute good throughout the pre-modern to early modern period. In the Edo period, copper was perhaps Japan's chief export, as the archipelago became the chief source of copper to the entire region.

Early Coinage

The Wadô era (708-715) is named after the significant discovery of copper seams in Musashi province; the era's name means literally "Japanese copper." Copper coins minted during that period based on the form of Chinese ones are believed to have been the first coins minted in Japan.

The Song Dynasty produced more copper coins than any other dynasty; in the 1070s, China was producing nearly six billion coins per year, a process which required 9600 tons of copper each year. Many of these coins made it to Japan, where Chinese coins remained a standard mode of exchange over domestically minted coins throughout much of the pre-modern period.

Muromachi Period

Though copper coins were for a time a major trade and tribute good, or form of payment, exchanged between China, Japan, Korea, Ryûkyû, and beyond, and indeed were one of Japan's major imports from China in the kangô bôeki "tally trade," the Ashikaga shogunate banned the outflow of copper coins from Japan in 1471, especially to Ryûkyû via Satsuma.

Though not comparable to production during the Song Dynasty, the Ming Dynasty, especially under the Yongle Emperor (r. 1402-1424), saw considerable minting of copper coins. Coins from the Yongle era circulated so widely in Japan that even today the character 「永」 (J: ei, C: Yǒng as in Yongle) is sometimes used to refer to copper coins (e.g. 「永二〇〇文」 , meaning 200 mon of copper coins).

Edo Period

Copper coins remained a common mode of exchange in this period, alongside gold and silver. Copper was typically measured by weight in momme, with around 100 copper coins being worth roughly one momme of silver.

The shogunate began promoting the export of copper more forcefully in 1695 as a substitute for silver, which was flowing out of the country at worryingly high rates. This export substitution was greatly successful for a time. Chinese merchants found the Japanese copper to be of high quality, and available for prices competitive with the Chinese market. Meanwhile, the Qing Dynasty government was minting around 40,000 piculs (J: kin, C: jīn, approx. 2,740 tons) of copper coins each year. Japanese copper was of higher quality than that produced domestically in China at the time, and would play a significant role in helping meet the Qing government's demand for over forty years, until in 1738, the Qing turned to relying more heavily on mines in Yunnan province, which had expanded their production and/or raised the quality of their output. Around this same time, at the end of the 17th century, the shogunate claimed exclusive authority to mint currency, putting an end to regional/domain production, and establishing its own shogunal gold, silver, and copper mints in Edo, Osaka, and Kyoto.

While copper mines operated in many parts of the archipelago in this period, the chief source of copper production was Akita han. Many of these mines saw considerable expansion in their production in the 17th century, but were well on the way to being exhausted by the end of that century, joined by Japan's silver mines not long afterwards.