A contribution by Iva Kolenković Močilac and Ana Maričić
On June 10th, 2022, after spending three days in the beautiful Luleå we took an afternoon train to Kiruna, the northernmost town in Kingdom of Sweden, located at the north of the Arctic circle. The journey lasted three hours, but we didn’t find it tiresome, since we enjoyed the beautiful scenery of Swedish wilderness that unrolled in front of our eyes.
Upon arriving to Kiruna on a sunny evening, we were stunned by its liveliness and cheerfulness. There were many people on the streets and the town was bathed in sunlight and saturated with interwoven melodies coming from many passing cars. The view of the town is dominated by two mountains – Luossavaara – which was an open pit until the 1960s, and Kiirunavaara, hiding the largest underground iron ore mine in the world (Figure 1). Kiruna is a small miners’ town with 17 000 inhabitants, most of whom are connected to the mining company.
Figure 1. The view of the Kiruna mine
On a walk to the hotel, we went through one of the abandoned blocks. The abandoned and silent buildings were in sharp contrast to the surrounding vivacity. We’ve read before that the western part of Kiruna town is being relocated approximately 3 kilometres towards the east, due to a risk from current underground mining operations. We were therefore not completely puzzled. Yet the abandoned buildings raised a certain feeling of discomfort. Many cultural heritage buildings and wooden houses have already been moved to a new location. They also plan on moving the old church, which is one of the largest wooden buildings in Sweden (Figure 2).
Figure 2. Church in Kiruna is one of the largest wooden buildings in Sweden
After a night of wonder upon the never-setting sun, we took a tour around the town. In the morning, the weather changed, and almost instantly the sunny town became sombre and murky. However, heavy rain and low temperature didn’t seem to influence its charm.
In the afternoon, we took a guided tour of the Kiruna underground mine. The bus picked us up in the tourist office in town and brought us 540 m below the ground to LKAB’s Visitor Centre (Figure 3) through the underground road that is wide enough so that two large vehicles can pass through at the same time. The only comment our guide made is that it is forbidden to use flash light during the bus ride because it could distract the driver.
Figure 3. LKAB’s Visitor Centre
Currently, the main level of the mine is at 1,365 m. The mine produces around 50,000t of ore feed material a day. Many of the processes are partly or fully automatized. Therefore, there are still around 400 employees working in the mine.
While in the visitors’ centre, deep in the underground, the guide explained to us that Kiruna ore body was formed 1,600 million years ago, resulting from intense volcanic activity with the precipitation of iron-rich solutions on a syenite porphyry footwall. The ore body was then covered by other volcanic and sedimentary rocks and tilted to its current dip of 50-60°. The ore consists of magnetite-apatite mix, with iron content surpassing 60%. The nice samples of magnetite and apatite can be seen in the mine cafeteria (Figure 4).
Figure 4. Entrance to the mine cafeteria in Visitor Centre
As of December 2019, it was estimated that the mine contained 208Mt of proved reserves and 408Mt of probable reserves. Considering current production rate, it is clear that the exploitation from Kiruna mine can be expected to continue in the coming decades.
The mine is divided into eight production areas, each containing its own group of ore passes and ventilation systems. The guide also described the exploitation process and the progress of exploitation works in the mine, using video materials and schematic cross-section of the mine (Figure 5).
Figure 5. Schematic cross-section of the mine
Using a remote-controlled drilling rig, the long holes are drilled in a fan-shaped pattern within the ore in the ceiling of the transport tunnels (drifts). An explosive is then pumped into the holes and blasted (blasting is done every night at 2 A.M.). The blasted ore is collected and transported via trains to large crushers where it is crushed into pieces of about 10 cm. The ore is then transported to the surface by ore elevators, the so-called skips (Figure 6). Each skip can transport 40t of ore at a speed of 60 km/h.
Figure 6. Skip for transporting ore to the surface
In addition, a 3D model of the town of Kiruna and the surface part of the mine are on display in the visitors’ centre (Figure 7). There, visitors can see which parts of the town are at risk due to exploitation. They are also shown a plan for the relocation of certain districts to new, more eastern locations of the town.
Figure 7. 3D model of the town of Kiruna
We were very thrilled to visit the town of Kiruna and the largest iron ore mine in the World, even if the visit only lasted for 24 hours. We definitely recommend a visit to the north of Sweden during the summer months when the sun never sleeps. The only thing we would like to warn visitors about is the blasting, which is carried out at 2 A.M and causes ground vibrations similar to minor earthquakes.
This article has been published in the June 2022 edition of the ENGIE Magazine.