Active underground polymetallic mine in the Boliden area, Skellefteå Municipality; Sweden's deepest mine, reaching 1,500 metres depth.
Renströmsgruvan is an underground mine extracting zinc, copper, lead, gold and silver ores, located approximately 15 kilometres west of Boliden village in Skellefteå Municipality, Västerbotten County, Sweden, within the Skellefte mining district. The deposit was first identified in 1926 when Renström East was intersected in drill holes, revealing two principal ore bodies. A mining test and a shaft sunk to the 469-metre level were carried out between 1944 and 1948.
Full production commenced in 1953, and the shaft was deepened to the 910-metre level in 1959. Owned and operated throughout by Boliden AB and its predecessors, Renströmsgruvan has been progressively deepened over subsequent decades, with new ore zones — including Simon (discovered 1998, in production 2000) and the Vilma and Julia lenses (encountered 2005, Vilma in production 2006) — sustaining operations far beyond originally anticipated mine life. In January 2019 the mine reached a depth of 1,500 metres, making it Sweden's deepest active mine.
The mine has a surface headframe and associated pithead infrastructure. Crushed ore is hauled to the Boliden Area Operations process plant for flotation treatment, with concentrates supplied to Boliden's Rönnskär smelter at Skelleftehamn.
Renströmsgruvan lies within the Paleoproterozoic Skellefte district of northern Sweden, a volcanic-hosted massive sulphide belt extending roughly 100 kilometres across Västerbotten County. The Renström mineralisation consists of several lenses characterised by massive to semi-massive pyrite-sphalerite dominated ores with subordinate chalcopyrite and local stringer-type sulphide mineralisation. Ores in the Renström area have higher zinc, gold, silver and lead contents and lower sulphur and arsenic content than most other volcanic-hosted massive sulphide ores in the Skellefte district.
The deposit was first intersected by drill holes in 1926, when Renström East was identified along with two subsequent principal ore bodies. Exploration and a mining test were conducted between 1944 and 1948, during which a shaft was sunk to the 469-metre level. Full production was achieved in 1953. The shaft was deepened in 1959 to the 910-metre level. The Boliden Area concentrator, commissioned in 1953 and rebuilt between 1989 and 1991, processes ore from Renström and other mines in the area. The concentrator rebuild increased capacity to 1.5 million tonnes per year and introduced autogenous grinding, large flotation cells, pressure filtration and a process information system.
Renström has been connected underground to the Petiknäs mine by rail haulage at the 800-metre level, a development described as a major investment in the Boliden Area Operations. The main recent capital project cited in sources was this Petiknäs–Renström underground rail link.
New ore zones continued to extend the mine's life well beyond early projections. The Simon zone was discovered in 1998 and entered production in 2000. In 2005 two additional sulphide lenses, Vilma and Julia, were encountered in the deep ore zone; Vilma entered production in 2006, with large-scale mining methods subsequently applied there. A gold leaching plant with a capital cost of SEK 100 million was commissioned at the Boliden Area process plant in 2001, initially to treat gold-rich ore from the Einarsson zone at Kristineberg but also benefiting Renström output.
In January 2019 Renström reached a depth of 1,500 metres — equivalent to more than four Eiffel Towers stacked vertically — making it Sweden's deepest mine. Exploration targets at depth were continuing to be developed at the time: drifts towards the 1,700-metre level were under development, with ore confirmed at that depth. Boliden implemented autonomous haulage technology at Renström in a collaboration with Sandvik, deploying AutoMine Underground for autonomous loader and truck operation during night shifts, allowing a single operator to control multiple machines simultaneously.
In 2024, around 1,781,000 tonnes of ore were processed from the Boliden Area mines as a whole, producing concentrates of zinc, copper, lead, gold, silver and tellurium. Mineral Resources at Renström increased in 2024 due to successful exploration drilling. By 2020, 14,493,000 tonnes of ore had been concentrated at Renström over the mine's lifetime at average grades of 2.7 g/t gold, 143 g/t silver, 0.7 per cent copper and other metals. Renström continues in active production as one of three underground mines in the Boliden Area, alongside Kristinebergsgruvan and Kankberg.