Osarizawa

尾去沢鉱山跡

飛鳥末期 708 年(和銅元年)の発見を起源とし、かつては金を産出して東大寺大仏建立や奥州平泉の発展に貢献したと伝えられます。 1598 年(慶長 3 年)盛岡藩士 北十左衛門の白根金山発見を発端にして尾去沢では金鉱脈の発見が相次ぎ、藩政期を通じて開かれた金山は 18 箇所に上りました。 17 世紀後半に金山の衰退が進みますが、1695 年(元禄 8 年)田郡における銅鉱の発見を転機にして銅山開発が各地で進められ、諸鉱山の運営は山師や商人による請負と藩による直営とで行われました。 尾去沢で生産された荒銅は大坂で精錬された後に長崎御用銅として海外との貿易決済に用いられ、幕末には別子、阿仁と並ぶ日本三大銅山と称されるまでに発展します。 明治期に入ると経営は変遷を重ねて 1889 年(明治 22 年)に三菱社へと移り、後に改組を経て設立された三菱合資会社の経営下で発電所の設置や鉱山の電化、選鉱場の新設が進められました。 その後、分社化された三菱鉱業が経営を引き継ぎ、戦時体制下では重要鉱物資源として増産が図られ、1943 年(昭和 18 年)に出鉱量 103 万 t を記録し、従業員数 4,486 名を数えて最盛期を迎えます。 1950 年(昭和 25 年)終戦後の財閥解体に伴い、金属部門を分離して設立された太平鉱業(後の三菱金属鉱業)が操業を続けますが、昭和中期に入ると海外における鉱山開発と過剰生産を受けて銅価格が下落し、操業規模の縮小を余儀なくされました。 1972 年(昭和 47 年)尾去沢鉱山株式会社を設立して事業を継続させますが、高品位鉱石の枯渇や輸入鉱石の増加、円高による銅価格の低迷から後に閉山を迎えます。 周辺には広大な敷地と巨大な施設跡が今も残ります。

1978 年閉山

Osarizawa Mine

According to legend, the mine was discovered in 708. In ancient times, mined gold contributed to the construction of the Great Buddha in Todai-ji Temple and the golden culture of Hiraizumi. After Juzaemon Kita, a feudal retainer of the Morioka Domain, discovered Shirane Gold Mine in 1598, gold veins were discovered in Osarizawa, and 18 gold mines opened in the period of domain duties. Although the gold mines waned in the late 17th century, copper ore was discovered at Tagori in 1695. Taking this opportunity, the copper mine development progressed throughout Osarizawa, and the mines were operated by mining engineers, merchants, and the domain. Crude copper was refined in Osaka and was used for trade settlement. Then the mine grew into one of Japan's three largest copper mines along with Besshi Mine and Ani Mine. In the Meiji period, mining rights were transferred several times, and Mitsubishi Company acquired the rights in 1889. Mitsubishi Limited Partnership, established by reorganization, proceeded with the establishment of power plants, electrification of the mine, and the construction of a new beneficiation plant. Subsequently, the mining department was separated as Mitsubishi Mining Company Ltd. and took over the management. The company increased production as important mineral resources in wartime. In the peak year of 1943, the mine produced about 1.03 million tonnes of ore, and the number of employees reached 4,486. After the war, the metal department became independent as Taihei Mining Co., Ltd., later Mitsubishi Metal Mining Co., Ltd., due to the dissolution of the big financial combines in 1950 and took over the operations. In the middle of the 20th century, the domestic price of copper declined owing to the mine development and overproduction in foreign countries. Accordingly, the mine reduced unavoidably the scale of operation. Although newly formed Osarizawa Mine Co., Ltd. inherited operations in 1972, the mine closed due to depletion of high-grade ore, demand for imported ore, and copper price stagnation caused by the strong yen. The large-scale mining facilities remain even now in the vast grounds.

closure in 1978

秋田県鹿角市尾去沢字獅子沢
銅、金、銀、鉛、亜鉛

Shishizawa, Osarizawa, Kazuno City, Akita
copper, gold, silver, lead, zinc

尾去沢では積極的に近代技術が取り入れられ、江戸末期には国内初の発破試験が行われました。 三菱による経営は鉱山に飛躍的な発展をもたらし、削岩機の導入や火力、水力発電所の設置が進められて全山電化が図られます。 広大な敷地には月産 10 万 t の処理能力を持つ国内最大級の選鉱場に隣接して長大な煙道と高さ 60 m の煙突を備えた製錬所が設けられ、周辺では煙害による森林の減少や消失が顕著となりました。

The mine introduced modern mining technology, and the first mine blasting in the country was experimentally performed at the end of the 19the century. Later, Mitsubishi advanced the electrification of the mine, such as introducing rock drills and constructing thermal and hydraulic power plants. The beneficiation plant was one of the largest in the country with a high processing capability of 100,000 tonnes per month. The neighboring smelter had large flues and a chimney with a height of 60 meters, causing a reduction in forests due to smoke pollution.

獅子沢地区
Shishizawa area

空中写真-獅子沢-1976年
© 国土地理院

1976 年(昭和 51 年)当時
At the time of 1976

空中写真-獅子沢-現在
© Google

現在の様子
The present state

The Remains Photographed in
Abandoned Osarizawa Mine

尾去沢鉱山-#01

#01

鉱山の一帯には東に西道、五十枚、南に赤沢、長坂、槙山、西に元山、田郡、北に崎山などの多くの鉱脈群が散在し、かつては各々が一つの鉱山として開発されました。

The mine had a large number of ore vein groups, such as Saido and Gojumai in the east, Akasawa, Nagasaka, and Makiyama in the south, Motoyama and Tagori in the west, and Sakiyama in the north. Each of them was independently developed as one mine until the late 19th century.

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尾去沢鉱山-#02

#02

尾去沢から北の米代川を挟んだ対岸に位置する白根金山には、古くより砂金にまつわる説話が残ります。 後に小真木鉱山と改称され、尾去沢鉱山の支山とされました。

Shirane Gold Mine, situated to the north of Osarizawa across the Yoneshiro River, has legends about alluvial gold mining. Later, the mine was renamed Komaki Mine and operated as part of Osarizawa Mine.

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尾去沢鉱山-#03

#03

周辺には多くの鉱員住宅の他、小学校や劇場、運動場、神社などの様々な施設を備えた鉱山町が築かれて賑わいました。 その一部は残され、現在も活用されています。

A mining town was built in the vicinity and comprised row houses for miners, an elementary school, a theater, sports grounds, shrines, and others. Some of them are utilized for other purposes and can be seen even now.

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尾去沢鉱山-#04

#04

1936 年(昭和 11 年)鉱山北部の中沢鉱滓ダムが二度にわたって決壊し、沢沿いの集落が泥流に襲われます。 300 戸近くが全半壊し、374 名の死者を出す大惨事となりました。

The Nakazawa Tailings Dam, situated on the northern side of the mine, collapsed twice in 1939, causing destruction of about 300 houses and 374 deaths.

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尾去沢鉱山-#05

#05

採掘対象とされた鉱脈はおよそ 560 条 24 鉱脈群に上り、大規模な鉱脈では走向延長 1,000 m を超えました。 坑道は深さ 30 m 毎に水平坑道が展開され、総延長は 800 km に達します。

The ore deposits consisted of 24 ore vein groups with a total of about 560 veins, and some of them had a length of over 1,000 meters. The mine tunnels were dug horizontally at 30 meters intervals of depth, and their total length reached 800 kilometers.

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尾去沢鉱山-#06

#06

三菱の経営下にあった約 90 年間に 2,850 万 t の粗鉱が採掘され、生産量は銅 30 万 t、金 4.4 t、銀 155 t、鉛 1 万 t、亜鉛 1 万 t ほどに及ぶと推定されます。

The mine produced about 28.5 million tonnes of crude ore, 300,000 tonnes of copper, 4.4 tonnes of gold, 155 tonnes of silver, and 10,000 tonnes of lead and zinc respectively for about 90 years under the management of Mitsubishi.

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