But silver mining in Gruveåsen had been established well before then, and was referred to as the Argenti Fodinæ (Latin for "The Silver Mines") in a source from 1532, Jacob Ziegler's book about Scandinavia. In 1539, a silver mining venture proper had been started by Christian III's with imported expert German miners. At the time, the newly discovered sea route to India and the Far East had prompted a scramble to search for silver to finance trade, but the Gruveåsen mines were then shut in the first half of the 1540s when the price of silver fell sharply due to large amounts of silver flowing from Spanish Latin America. The price of silver eventually recovered in the latter half of the 16th century on increased demand for currency to pay for luxury goods from China, where the Portuguese built Macau in 1555, and the Far East. So, when admiral Ove Gjedde returned from a long journey 1618-1622 from Ceylon and India where he had established a trading outpost at Trankebar, now Tharangambadi, on the Coromandel Coast of south-eastern India, as part of Christian IV's plans to build a Danish East India Company, Gjedde was sent to Norway to develop the mining industry. And it was Gjedde who re-started silver mining in the area proper in 1623, which in the following year, when King Christian IV came to Norway to visit and also founded the town of Kongsberg, by royal charter were formally established as Kongsberg Sølvverk. The King's Mine ("Kongens gruve") was the largest mine at Kongsberg. The operation of the plant reached its peak in the 1770s when over 4,000 people were directly involved in the production. The 1750s, 1760s and 1770s were the heyday of the silverworks. Significant new ore discoveries were made, especially in the 1830s and 1860s. The particularly rich King's mine was operated to a depth of over 1,000 meters. The plant extracted silver right up until the closure in 1957.