Kongsberg Silver Mines
Kongsberg Silver works ( Kongsberg Sølvverk) was a mining operation at Kongsberg in Viken county in Norway. The town of Kongsberg is the site of the Norwegian Mining Museum (Norsk Bergverksmuseum).
Operating from over 80 different sites, Kongsberg silver mines constituted the largest mining field in Norway. It was the largest pre-industrial working place in Norway, with over 4,000 workers at its peak in the 1770s and supplied over 10% of the gross national product of the Danish–Norwegian union during its 335-year-long history: over 450,000 man-years were expended in the production. The silver mines in Kongsberg were in operation from 1623 until 1958. Total production exceeded 1,3 million kg silver. 
Silver was first discovered between the 1 July and 5 July 1623, according to the somewhat romanticized story, which tells of two small children - Helga and Jacob - who were out shepherding their cattle at the top of Gruveåsen hill. They had an ox with them which scraped on the side of the mountain. They could see something shining and glimmering, and they picked it up and took it home to their father. Recognizing it as silver and quite valuable, he melted it and brought it to the town of Skien in Telemark county to sell it. In Skien he was arrested, the police finding it suspicious that someone would attempt to sell silver at such a low price. Being convinced that he was a thief, he was given the choice between telling where he had found the silver, or being sentenced to hard labour. He chose to tell the authorities he had found the silver in Southern Sandsvær, which was the old name for Kongsberg.