Mining in the Edo period

Call the "Land of Gold" by Marco Polo, Japan was blessed with mineral resources, such as gold and silver, and forest resources that were converted to fuel, and was considered to be one of the world's leading mining countries since before the Edo Period. The Edo government actively promoted the mining industry, establishing mines throughout the country. Copper production was the highest in the world, and products were distributed internationally via Nagasaki.

This is acolor development technique which draws out the gold color in gold and silver dlloy and has proven to be moredurable than planting. During the Edo period, the ratio of gold to silver in the koban varied from year to year, leading to the possibillity of some obans and kobans haveing a stronger silver appearance than other. This redying technique was performed to alleciate this situation. It is said that the use of this method is cofirmed in ancient Inca artwork. According to Japanese tradition, however, this method is believed ti have been passed down as the secert medhod employed by the methalsmith "Goto Shirobei-Ke" and was used in Obanza and Kinza (oban and gold mint). Literatures use the, irotsuke (dying), and later iroage (redying). With this method, the koban is coated with a dye and heated, the silver portion is extracted from the gold and silver surface, and the remaining gold is recrystallized to form a gold-enriched layer.