The town of Røros owes its very existence to more than 330 years of copper mining (1644–1986) by Røros Kobberverk. More than 6.5 million tonnes of ore were produced from over 12 mines, with average grade 2.7% copper and over 4.2% zinc. In the long history of mining, zinc was only extracted in the final 4–5 years of operation at the Lergruvbakken mine. An estimated 250,000–300,000 tonnes of zinc was not recovered across all the mines, and remains in the ground or unprocessed on dumps.The existing plant site was constructed in 1968 and was operational from 1973 to 1977, when Røros Kobberverk closed down. Production continued at the Killingdal mine, operated by Killingdal Grubeselskab, until 1985. Since then, there has been no production; however, drillcore going back to the 1950s is available for resampling, together with exploration data and production records.