Silver mining at Mikobata began over a 1,000 years ago. By the fifteenth century, Mikobata had joined Akenobe and Ikuno as one of the most productive mines in the region. Its most prosperous decades were during the early Meiji Period (1868–1912), from the late 1870s to the mid-1890s. In 1896 the mine was sold to the Mitsubishi Company, but by 1907 its silver and copper were mostly exhausted. In 1919 Mitsubishi transformed the site into one of East Asia’s largest ore processing plants. Raw ore containing zinc, copper, and tin was shipped by rail through the mountain from Akenobe, where new veins had been discovered.
The Mikobata processing plant was built on a steep slope. Ore was delivered to the top, where it was crushed and mixed with water to form slurry. As the slurry continued downhill, it was separated using a variety of physical and chemical processes. At the bottom of the hill, waste water was removed, leaving the minerals behind. The water was then fed into huge cement funnels known as thickeners. These condensed the waste water into a thick sludge.
The plant closed in 1987 and was partially demolished in 2004, leaving only the concrete foundations and thickeners.