Finland's largest underground mine and the EU's sole chromite producer, operating at Elijärvi in Keminmaa with a prominent hoisting tower on surface.
Elijärven kaivos, also known as Kemin kaivos, is an active chromite mine located at Elijärvi in Keminmaa municipality, north of the city of Kemi. Owned by Outokumpu Chrome Oy, a subsidiary of Outokumpu Oyj, it is the only chromite mine in the European Union and Finland's largest underground mine by annual ore output, with a production capacity of 2.7 million tonnes per year. The deposit was identified in 1959–1960 following the discovery of chrome-rich boulders near a freshwater canal excavation.
Outokumpu began developing the site in 1964–1965 and open-pit extraction started in 1968. Open-pit working continued until 2005, reaching approximately 200 metres depth. Underground operations began in 2003 and the mine transitioned entirely to underground working that year.
A major expansion programme, DeepMine, extended the underground workings from 500 metres to one kilometre depth by 2022 at a cost of EUR 280 million. The ore is processed on site and chromite concentrates are transported to Outokumpu's ferrochrome plant at Tornio for integration into the stainless steel production chain.
The chromite deposit at Elijärvi, Keminmaa came to light on 30 June 1959, when samples gathered near a freshwater canal excavation project were submitted to the Geologian tutkimuskeskus (Geological Survey of Finland). One sample proved highly chrome-rich. The find was made by diver Martti Matilainen, and the actual ore body was located in the Elijärvi area by spring 1960 under the direction of geologist Aarno Kahma.
After completing its preliminary research, the Geological Survey handed the deposit over to Outokumpu Oy, which continued investigations until 1962. Ore reserves were estimated at the time at approximately 30 million tonnes. In autumn 1964 Outokumpu took the decision to develop the Kemi chromite deposit.
Road construction from Perta-aapa to Elijärvi began in autumn 1965, and earthworks on the future mine site commenced simultaneously. Open-pit extraction began in 1968. The pit eventually reached approximately 200 metres in depth.
The ore body has a nearly vertical dip, an average thickness of approximately 40 metres, and extends over about one kilometre in length. The chromium oxide content of the ore averages 26 per cent, with a chromium-to-iron ratio of 1.6. Underground production began in 2003, initially from the 500-metre level, with the open pit continuing in parallel.
The mine fully transitioned to underground operation as open-pit extraction ceased in 2005. Underground ore is transported by incline or shaft. Ore is crushed underground and conveyed to pre-crusher silos near the shaft, then hoisted via a 70-metre-high winding tower to the surface processing plant, where it is separated into lump concentrate and fines concentrate for rail transport to Tornio.
A dedicated mine railway branch, the Elijärven kaivosrata, connected the mine to the Oulu–Tornio main line; rail ore haulage on this branch ended on 31 December of an unspecified year following the conversion to road transport. In late 2017, Outokumpu launched the DeepMine expansion project, designed to deepen the underground mine from the 500-metre level to a new principal level at approximately 1,000 metres depth. The project had a budget of approximately EUR 280 million.
Construction of a new 76-metre-high (subsequently reported as 80-plus metres or 104 metres in contract documents) hoisting tower was part of this programme, contracted to NCC at a value of approximately EUR 13.6 million. DeepMine was completed in 2022–2023, bringing the shaft depth to one kilometre. Outokumpu also committed to making the Kemi mine carbon-neutral by 2025, replacing fossil fuels in machinery and vehicles with renewable fuels supplied by Neste, a step estimated to reduce annual greenhouse gas emissions by 11.3 million kilograms.
Known ore reserves are reported at approximately 50 million tonnes, with mineral resources estimated at approximately 98 million tonnes to one kilometre depth; geological indications suggest the ore body continues to at least two to three kilometres depth. The mine employs approximately 550 people daily, a mix of Outokumpu staff and contractors, and forms a critical link in the integrated production chain from chromite ore to stainless steel at Outokumpu's Tornio steelworks.