Ashio Copper Mine

Japan's largest copper mine, which was the birthplace of the Furukawa zaibatsu. Located in Ashio-cho, Nikko City, Tochigi Prefecture. Until its closure, the mine produced 1,900 ore veins and 130 kajika (mainly massive replacement deposits), and was also famous for producing a wide variety of minerals.

Developed in the mid-16th century, the Shogunate started direct mining in 1610 (Keicho 15), and with the rapid increase in copper production from the late 17th century, the Copper Mine Highway was opened, and the area prospered, supplying one-fifth of the copper exports of Nagasaki (Gogaichi Copper). However, the mine declined due to the operation of the mine by weak miners and repeated floods. For this reason, it was not selected as a government-run copper mine at the beginning of the Meiji era. In 1877 (Meiji 10), Furukawa Ichibei began redevelopment with the cooperation of Shiga Naomichi (Naoya's grandfather) and Shibusawa Eiichi, and in 1883, he succeeded in capturing Onaori (rich ore section) at Honzan. In response to the rapid increase in copper production after that, Western technologies such as hydroelectric power generation were adopted one after another. At the same time, the Watarase River Copper Pollution Incident occurred.

From the middle of World War I, huge nodules containing 82,000 tons of copper were discovered one after another in the Tsudo mine, and the mine overcame the copper recession that followed after the war, reaching a peak of 15,000 tons of copper production per year. However, during the Pacific War, the mine was forced to prioritize production, and it went into decline due to reckless mining and a lack of materials. It took some time to recover after the war, but when the price of copper soared during the Korean War, the mine was streamlined and 500 employees were laid off. Immediately after that, the redevelopment of the upper and lower parts of the mine improved, and in 1956 (Showa 31), copper smelting was carried out using a groundbreaking flash smelting method, and sulfuric acid production was started to make exhaust gas harmless, preventing mine pollution. The mine set a record of 500 tons of copper production per month. However, with liberalization, the mine's upper ore sources were depleted and working conditions worsened, and the mining division was closed in February 1973. Imported ore continued to be refined thereafter, but with the closure of the JNR Ashio Line, refinery was effectively halted in 1989. Crude copper production was about 150,000 tons before the Meiji period, and over 670,000 tons from the Meiji period until the mine closed, totaling 820,000 tons.

[Yasumasa Murakami]

“Ashio Copper Mine History” by Yasumasa Murakami (2006, Zuisosha)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

古河財閥発展の母胎となった日本最大の銅山。栃木県日光市足尾町に所在。閉山まで鉱脈1900本と130個の河鹿(かじか)（主として塊状交代鉱床）を稼行、多彩な鉱物の産出でも著名である。

　16世紀半ばから開発され、1610年（慶長15）から幕府直山、17世紀後半からの産銅急増で銅山街道を開設、長崎輸出銅の5分1（五ヶ一銅）を供給、繁栄した。しかし弱小銅山師による銅山稼行と度重なる水害によって衰退した。このため明治初めの官営銅山の選から外れた。1877年（明治10）古河市兵衛は志賀直道(なおみち)（直哉の祖父）や渋沢栄一(しぶさわえいいち)の協力を得て再開発に着手、1883年に本山(ほんざん)で大直利(おおなおり)（富鉱部）捕捉に成功、以後産銅が急増したのに対応して、水力発電などの欧米技術を次々に採用した。それと同時に渡良瀬川鉱毒事件が発生した。

　第一次世界大戦半ばから通洞(つうどう)坑で総計含銅量8万2000トンに及ぶ巨塊状河鹿を相次いで発見、大戦後から続いた銅不況期を乗り越え、年産銅1万5000トンのピークを記録した。しかし太平洋戦争期には生産第一主義を強制され、乱掘と資材不足から衰退の途を辿った。戦後の復興には手間取ったが、朝鮮戦争による銅価高騰時に鉱山のスリム化と500名の人員整理を断行。その直後から上部再開発と下部開発が好転、1956年（昭和31）には画期的な自熔製錬法による銅製錬と排煙無害化を図る硫酸製造を開始して鉱害防止も達成。月産銅500トンの記録を打ち立てた。しかし自由化とともに上部鉱源枯渇と下部の労働条件悪化から、1973年2月鉱山部門が閉じられた。以後輸入鉱製錬が継続されたが、国鉄足尾線の廃止に伴い、1989年製錬を事実上中止した。粗銅生産量は、明治以前が約15万トン、明治から閉山まで67万トン余、総計82万トンに達した。

［村上安正］

『村上安正著『足尾銅山史』（2006・随想舎）』

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