A total of 11 mines located in the upper Ani River basin are collectively called "Ani Mine" and produced gold, silver, and copper ores.
According to lore, the origin is the discovery of alluvial gold at Yukuchinai in 1309.
Then the development of gold and silver mines, such as Mukaiyama and Shichijumaiyama, brought prosperity to Ani from the end of the 16th century.
However, these mines waned in the second half of the 17th century.
Kitaguniya, an Osaka merchant, discovered copper ore deposits at Gokuinzawa in 1670, which led to the development of the copper mines in Ani.
At that time, the shogunate switched exports from silver to copper and promoted copper mining to prevent the outflow of gold and silver overseas.
Accordingly, Osaka merchants, such as Osakaya and Izumiya, began mineral exploration in Ani, discovering six copper mines, namely, Kosawa, Sanmai, Kayakusa, Magisawa, Ninomata, and Ichinomata, by the early 18th century.
Subsequently, the Akita Domain took direct control over the copper mines in 1702 and sent crude copper to Osaka, where the copper was managed by Doza.
Then the shipments from the domain reached their peak in the 1700s and accounted for 40 percent of the crude copper gathered from all over the nation for Osaka.
The prosperity continued until the 1760s.
Later, Osakaya contracted to manage the mines, and its operation continued until the second half of the 19th century.
In the Meiji period, the mine management was taken over by others several times, and it came under the control of the Meiji government in 1875.
Although the government introduced modern equipment to the mines as part of a policy, these efforts yielded no results.
Thereupon, the six copper mines and Mukaiyama Silver Mine were sold as part of the government property disposal to Ichibei Furukawa, the founder of Furukawa Mining Co., Ltd., in 1885.
Afterwards, the mines were restored through the efforts of Furukawa and prospered in the early 20th century.
Although operations at Ani Mine were suspended due to a decrease in resources in 1931, they were resumed two years later following the discovery of Nijushiko Gold Mine by Furukawa Ringyo-bu General Partnership.
After the war, the mine increased its production and streamlined operations in anticipation of trade liberalization.
As a result, the annual crude ore production exceeded 100,000 tonnes from 1958 onwards.
The company suspended operations again in 1970 and initiated a three-year mining exploration.
The exploration led to the discovery of new ore deposits, and the company established Ani Mine Co., Ltd. and transferred its operations.
The remains of a beneficiation plant, built in 1938, can be seen even now at Kosawa.
The Meiji government invited Adolph Mezger and other mining engineers from Germany with the aim of mine modernization.
In 1884, they completed a connecting adit called 'Sanmai-Tsudo' between Sanmai and Kosawa, enabling the gathering of ores from each copper mine to Kosawa.
Additionally, an exclusive railway line was constructed to transport concentrates from Kosawa to Mizunashi Smelter.
As a result, scattered mining facilities and distribution were centralized at Kosawa, causing the disappearance of long-established settlements around each mine.
Later, Furukawa acquired modern mining equipment and engineers in addition to the mine and carried out operational reforms throughout the Meiji period.
Besides the discovery and development of ore deposits, various initiatives increased production in the early 20th century, which included expansion of smelting equipment, construction of power plants and beneficiation plants, and the installation of steel rails.
In 1917, the mine employed 3,560 miners, producing 50,319 tonnes of crude ore and 1,307 tonnes of crude copper.
The crude copper was transported by cargo ships known as "Kitamae-Bune" from Noshiro Port.
Osaka-Doza gathered crude copper from all over the nation and manufactured copper ingots through a refining method called "Nanban-buki" by refineries called "Dofukiya".
Most of the ingots were exported from Dejima in Nagasaki to the Netherlands and Qing China.
The shogunate granted exclusive refining rights to "Dofukiya" in Osaka.
The Akita Domain was granted permission by the shogunate and established Kagoyama Refinery in 1775, consigning Osakaya to refining operations.
The refinery enabled the domain to extract silver from the crude copper and then engaged in illegal coin minting in the middle of the 19th century.