The mine at Loos in central Sweden was developed after 1736 by Henric Kalmeter. While searching for copper he discovered the area was a source of cobalt, which was valuable as a blue colouring for ceramics, enamels and glass. In 1745 he opened a mill for grinding pigment. He employed up to 160 people and exported cobalt blue pigment across Europe. In 1751, Baron Axel Fredrik Cronstedt isolated a previously unidentified element in ore from the Loos mine: nickel. The manager of the mill established a glassworks in 1763 but the mineral reserves were declining and the mine and mill closed in 1773. Volunteers began exploring the mine in 1989 and reopened it in 1992. After an introductory film at the surface, visitors go underground on timber staircases through rock-cut tunnels and caverns that follow the ore loads. Displays tell the story of Kalmeter and the mine with examples of minerals and glasswares.