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古遠部鉱山跡

鉱山が位置する県北東部の一帯は、かつては国内有数の黒鉱の産地として知られました。 黒鉱とは海底の火山活動に伴って形成される複雑硫化鉱であり、難処理性を特徴とする一方、成分中に様々な有価金属を含むため、その重要性は 20 世紀半ばから鉱業技術の発展とともに高まりました。 三菱合資会社は 1910 年（明治 43 年）に古遠部川上流の山間に採掘鉱区を設け、翌年に四熊沢と曲屋沢、1934 年（昭和 9 年）に鍋窪沢で小規模に坑道探鉱を行いました。 終戦の翌年から探鉱調査が再開されますが、有益な発見に至ることなく、長い期間が経過しました。 こうした中、隣接鉱山における新鉱床の発見を受けて 1958 年（昭和 33 年）から試錐探鉱が進められ、翌年から 1962 年（昭和 37 年）にかけて湯ノ沢、大黒沢、曲屋沢に相次いで黒鉱鉱床が発見されました。 起業工事の完成に伴い、古遠部は尾去沢鉱業所の支山として 1963 年（昭和 38 年）に試験操業を開始し、2 年後に古遠部鉱業所として発足を迎えました。 さらに、1968 年（昭和 43 年）に東又沢鉱床が発見され、翌年に竪坑の新設や選鉱設備の増強工事が進められました。 生産は順調に拡大し、最盛期となる 1972 年（昭和 47 年）の月産粗鉱量は最大で 16,000 t に及び、従業員数は 273 名を数えました。 同じ頃、三菱金属は石油危機による非鉄金属市況の低迷を受けて事業の再編を図り、1976 年（昭和 51 年）に保有鉱山を分社化します。 新たに設立された古遠部鉱業のもと、事業は南古遠部鉱山の名称で継続され、月産 13,000 t 前後の粗鉱量を維持しますが、後に鉱石の品位低下や円高の影響を受けて閉鎖されることとなります。 1984 年（昭和 59 年）までの出鉱量は 317 万 t に上り、開発当初の可採鉱量 181 万 t を大幅に上回りました。 古遠部川の沿岸には選鉱設備や竪坑を備えた鉱山事務所跡が現在も残ります。

1986 年閉山

Furutobe Mine

The mine was located in the northeastern part of the prefecture, which was known as Japan's largest Kuroko mining area. Kuroko is a black-colored complex sulfide ore formed by submarine volcanic activity. Although the ore is characterized by difficulties in ore dressing and smelting, it contains various valuable metals and gained importance with technological developments in the mining and smelting industries from the middle of the 20th century. Mitsubishi & Co. acquired mining rights for an area in the upper Furutobe River basin in 1910, and conducted small-scale tunnel exploration at Shikumazawa and Magariyasawa the following year, and at Nabekubosawa in 1934. Although mineral exploration was intermittently resumed from 1946, it yielded no significant results for many years. In 1958, taking advantage of the discovery of ore deposits at a neighboring mine, full-scale test boring began. As a result, the company successively discovered Kuroko deposits at Yunosawa, Okurosawa, and Magariyasawa from 1959 to 1962. With the completion of mine development in 1963, the mine began trial operations as part of the Osarizawa mining operations and became an independent operating unit of the company two years later. The company discovered Higashi-Matasawa deposit in 1968 and began its development in the following year, which included the construction of a new vertical shaft and the expansion of beneficiation capacity. Production increased steadily and, in the peak year 1972, reached a maximum of around 16,000 tonnes of crude ore per month, with a workforce of 273 employees. Meanwhile, Mitsubishi initiated rationalization due to a slump in the nonferrous metals market after the oil crisis and, in 1976, spun off all of its mines into separate companies. Accordingly, operations continued as Minami-Furutobe mine in 1976 under the management of newly established Furutobe Mining Co., Ltd. Although the mine maintained a stable production of around 13,000 tonnes of crude ore per month, it was later closed due to a decline in high-grade ore and the strong yen. Total crude ore production until 1984 reached 3.17 million tonnes, significantly exceeding the recoverable reserves, which were estimated at 1.81 million tonnes at the beginning of development. The remains of the mine office with a vertical shaft and beneficiation equipment can still be seen today.

closure in 1986