The Amount of Earth Moved through Iron Sand Mining (kannanagashi) and the Production of Iron Sand Smelting (tatara) in the Chugoku Mountains

Abstract

It is the purpose of this paper to estimate the amount of earth moved through Kannanagashi and the output of tatara in the Chugoku Mountains from historical data. In Japan iron was produced only by the traditional ironsand smelting method, tatara, until Western style smelting was introduced in 1853, and the tatara method continued to operate until the 1920s. The ironsand used as raw material is found in small quantities in weathered granitic rocks, it was collected by cutting weathered rocks and sorting in running water. This method of mining was known as kannanagashi. Spurs and hills in the Chugoku Mountains have been deformed by kannanagashi on a large scale as the quantities of ironsand found were small in proportion to the amount of earth moved. The amount of earth moved and the output of tatara can be estimated for the period of about 220 years from the beginning of the 18th century to the 1920s using the following factors: 1) the ratio of volume of iron sand collected to that of earth cut, 2) the volume of ironsand collected at one mine for one year, 3) the number of mines, 4) the ratio of iron sand used for tatara to output of tatara, 5) the volume of ironsand used for one tatara for one year, 6) the out put of one tatara for one year, and 7) the number of tatara. From the above calculations I conclude that the amount of earth moved was about 1,508 million m^3 and the output of tatara was about 2,660,000t.