World's largest underground iron ore mine, actively operated by LKAB at Kiirunavaara in Swedish Lapland, with an underground visitor centre at 540 metres depth.
Kiirunavaara Mine, operated by Luossavaara-Kiirunavaara Aktiebolag (LKAB) at Kiruna in Norrbotten County, is the largest underground iron ore mine in the world. The ore body, composed predominantly of magnetite, extends approximately 4 kilometres in strike length, averages 80 to 120 metres in thickness, and dips eastward at around 60 degrees, reaching depths in excess of 1,300 metres. Mining began in 1898 under open-pit methods and transitioned to fully underground sublevel caving from 1962.
LKAB was founded on 18 December 1890, and Hjalmar Lundbohm, appointed as site director in 1898, is credited as the founder of Kiruna, which developed as a planned industrial town from 1900. The Malmbanan railway reached Kiruna in 1899 and was extended to Narvik in November 1902, enabling bulk ore export to European ports. Since production began, the mine has extracted more than 950 million tonnes of ore.
Mining-induced subsidence led to a decision in 2004 to relocate Kiruna city centre, and the urban transformation has been under way since. LKAB operates an underground visitor centre at the 540-metre level.
Ore at Kiirunavaara had been known to the indigenous Sámi population for generations before Swedish authorities were formally informed. In 1696 a bookkeeper at the Kengis works noted rumours of iron in the two hills Luossavaara and Kiirunavaara. A Sámi man named Mangi informed Swedish authorities in 1736, receiving 100 riksdaler and lifelong tax exemption in return.
Systematic prospecting followed, but the absence of transport infrastructure and the extreme Arctic climate prevented any organised exploitation for a further century and a half. In the 1880s trial borings were made at Kiirunavaara. LKAB was constituted on 18 December 1890 following an initiative by Robert Schough and the involvement of K. A. Wallenberg.
The initial investors sold their stake in 1893 to Aktiebolaget Gällivare Malmfält because of the heavy capital requirements and the lack of early revenue. Hjalmar Lundbohm assumed direction of operations at Kiruna in 1898 and conducted the first systematic geological investigations of the ore body that year. Open-pit extraction began in 1898.
Lundbohm oversaw the founding of Kiruna as a planned settlement in 1900, and his first managing director's tenure continued until 1920. A provisional railway connection from Kiruna to Luleå opened in 1899. After Parliament approved a line to Norway in 1898, the Malmbanan was completed to Narvik in November 1902 and formally inaugurated by King Oscar II on 14 July 1903.
The railway provided the essential transport link for bulk ore export and was electrified between Kiruna and the Norwegian border in 1915. Open-pit extraction of the upper ore body continued into the twentieth century, but the open pit grew progressively larger and steeper. The summit of Kiirunavaara, known as Statsrådet at 247.7 metres above lake Luossajärvi, was blasted away in 1910 to facilitate mining.
In the early 1950s the transition to underground methods began, with a mixed open-pit and underground operation through the decade; from 1962 open-pit working was abandoned entirely. The exhausted open-pit void was subsequently backfilled with waste rock from underground operations. Underground mining employs sublevel caving, with sublevels spaced approximately 28.5 metres apart.
Ore is crushed underground and hoisted to surface for processing through sorting plants, concentrators, and pelletising plants. Finished pellet and sinter fines products are conveyed by rail on the Malmbanan to either Narvik or Luleå for shipment. By 1999 the principal haulage level was at 775 metres below the original ore outcrop.
In October 2008 LKAB decided to develop a further haulage level at 1,365 metres depth, which was completed in 2012 at a reported cost of approximately USD 1.7 billion, and is expected to support production to around 2035. As of 2020 the main production level operates at 1,365 metres. More than 950 million tonnes of ore have been extracted since 1898, and the deposit is estimated to contain proven and probable reserves exceeding 730 million tonnes at around 41 percent iron.
In January 2023 LKAB announced that the Per Geijer deposit adjacent to Kiirunavaara contains the largest known rare earth element resource in Europe. Mining-induced ground deformation was recognised in the 1950s, and subsidence cracks were found approaching the city centre by 2004, leading to LKAB's announcement that a major part of Kiruna would need to be relocated. The urban transformation programme has been under way since, with the new city centre inaugurated and the historic Kiruna Church moved to a new site.
LKAB operates an underground visitor centre, the InfoMine, at the 540-metre level, accessible by bus directly into the mountain.