It is not clearly known when iron was first manufactured in Japan. However, general consensus has it that the first iron was manufactured from magnetite sand. Seki City in Gifu Prefecture has long been noted for its production of excellent Japanese swords, and its site of an ancient forge probably dates from the end of the Kamakura period (1192-1333). I have applied chemical analyses to the irondregs from this site and found some interesting clues as to the nature of the ore used by the ancient swordsmiths as well as to the location where such ores were procured.
It is almost certain that the ore is not the pyrites (FeS2) found in the neighbourhood of the site, for the amount of S contained in the dregs is extremely small. We may ascertain that the ore was identical with the magnetite sand from Sanyin District, along the Japan Sea coast, on account of the low percentage of Ti contained therein, for the Sanyin, iron sand contains the lowest amount of Ti of all the similar sand in Japan.
It was also discovered that the pile of iron scraps at the bottom of the River Yamaura flowing through the City of Seki was not the natural product of the riverbed, but was dumped there as refuse. I subsequently analyzed the content of some ancient iron products such as iron nails found at the Hachiman Shinto Sanctuary, dating from 1758, and at the Miroku Buddhist Temple, dating from the Hakuho era (672-685), and found that the original ore was also magnetite sand. It is believed that in the Kamakura period, swordsmiths from Kyushu and Nara migrated to Seki, before the city acquired a fame for its manufacture of Japanese swords. The reason for this migration, according to one theory, was that the clay produced in this district was of superior quality for the purpose of firing the swordblades. So I analyzed the red clay taken from the same site, and the results were identical in the amount of alkali contained with those of Mr. TILDEN (published in Fay East, 1897) who analyzed the clay of Inariyama and Fukakusa, Kyoto, the clay popularly used as a medium for oxidized iron.
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