Finland and Sweden
Under the Nordic shield
The old bedrock of Finland and Sweden has been drilled for ore for more than a century. The two geological surveys, GTK in Finland and SGU in Sweden, keep registers of the drill holes whose core and logs came into public hands, and both publish them as open data.
That gives {holes} holes you can see here, almost all of them diamond-drilled for core. Most were drilled by state companies, mining companies and the surveys themselves decades ago, long before today's owners. This tour flies you through the ore fields behind them, then hands you the controls.
1900s to today
A century of core
Watch the holes arrive year by year. A few date from before the Second World War. Drilling took off in the 1950s and peaked in the 1980s, when about 13,000 of these holes were drilled, much of it by state-owned explorers such as Outokumpu, GTK and SGU working across the north.
After that the archive thins out: {d1990} holes in the 1990s, {d2000} in the 2000s and {d2010} in the 2010s. Drilling carried on, but most recent company holes stay in company databases and only some of their core reaches the national archives. Another {d0} holes have no year, so they only show when the year filter is open.
Kiruna
Viscaria, in the shadow of the iron mountain
Kiruna is famous for LKAB's Kiirunavaara, the giant iron ore body that is mined deep underground and is the reason parts of the town are being moved. LKAB's own mine drilling is not in this archive, so only a handful of holes sit on the iron mountain itself.
A few kilometres west is Viscaria, a copper deposit mined from 1982 to 1997, first by LKAB and then by Outokumpu. Its 2,600 or so archived holes make it the most densely drilled spot in this tour, and a new company is now preparing to mine copper there again. {site}
Gällivare
Malmberget and Aitik
Next to Gällivare are two very different mines. At Malmberget LKAB works a cluster of iron ore bodies underground. The archived LKAB holes here carry the names of the ore bodies, such as Hedvig and Sparre, but no drilling dates.
South-east of the town is Boliden's Aitik, a huge open pit for copper with gold and silver and Sweden's largest mine. The open-file holes around it were mostly drilled by NSG and Boliden in the 1980s. {site}
1924
The Skellefte field
On 10 December 1924 prospectors found a rich gold ore at Fågelmyran, west of Skellefteå. The Boliden mine that followed ran until 1967 and gave its name to the company. The same volcanic belt holds dozens of massive sulphide deposits of zinc, copper, lead, silver and gold.
Boliden still mines the belt, at Renström, Kristineberg and Kankberg among others. Here at Renström the archive holds Boliden's deep holes from the 2000s, while at Kristineberg, at the western end of the belt, the holes go back to SGU's survey drilling of the 1930s. {site}
Under the mountains
Laisvall and Stekenjokk
Along the edge of the Scandinavian mountains the ores are younger and different. At Laisvall, lead and zinc sit in flat sandstone beds. A boulder found in 1938 led to the mine, which ran from 1943 to 2001 and was for a time Europe's biggest lead mine. Most of its archived holes date from the 1940s and 1950s.
Further south, close to the Norwegian border, Stekenjokk was mined for zinc and copper from 1976 to 1988 after decades of SGU drilling. Across the border, Norway has a long mining history of its own, but NGU does not publish exploration drill holes as open data, so the map stops at the frontier.
Bergslagen
Falun, Garpenberg and Grängesberg
Central Sweden's Bergslagen is one of the oldest mining regions in the world. The Great Copper Mountain at Falun was worked for about a thousand years until the last blast in December 1992, and it became a UNESCO World Heritage Site in 2001. Research shows mining at Garpenberg, which Boliden still works for zinc, lead and silver, as early as 375 BC.
At Grängesberg, apatite-rich iron ore was mined until 1989. The 770 or so holes there, mostly from the 1960s to the 1980s, make it the busiest drilling site in southern Sweden. {site}
1908 to 1910
Outokumpu: following a boulder
In 1908, men dredging a shipping channel in eastern Finland pulled up a large boulder rich in copper. The geologist Otto Trüstedt spent almost two years tracing where the ice had carried it from. In March 1910 a diamond drill hit the ore at Outokumpu.
The mine ran until 1989 and gave its name to one of Finland's biggest companies. The holes here are Outokumpu's own, from the 1920s onwards, and the dataset's oldest Finnish holes are among them. {site}
1958
Pyhäsalmi and Vihanti: zinc in the middle of Finland
In 1958 a farmer digging a well at Pyhäsalmi struck rusty, weathered sulphide ore. Outokumpu opened a mine in 1962 and it went on below a kilometre deep before mining stopped in August 2022.
To the north-west, Vihanti was mined for zinc and copper from 1954 to 1992. Both mines sit in the same belt of old volcanic rocks, and both are ringed by Outokumpu's holes. {site}
Black schist nickel
Talvivaara and Terrafame
At Talvivaara, in Sotkamo, nickel, zinc, copper and cobalt are spread thinly through black schist. GTK drilled it in the late 1970s and 1980s, and decades later the low-grade ore was opened up in 2008 by leaching huge heaps of crushed rock.
The first owner ran into trouble and the state-backed company Terrafame took over the mine in 2015. All of the open-file holes here predate the mine. {site}
Central Lapland
Kevitsa, Kittilä and the Sakatti gap
GTK's work in Lapland found Europe's largest gold mine. Gold was found at Suurikuusikko near Kittilä in 1986 and Agnico Eagle has mined it since 2008. Near Sodankylä, Outokumpu and GTK drilled more than 800 holes at the Kevitsa nickel-copper body, which opened as a mine in 2012 and has been Boliden's since 2016.
Some famous names are missing. Anglo American's Sakatti copper-nickel discovery, confirmed in 2009 north of Sodankylä, and modern mine drilling at Kemi chrome and Siilinjärvi phosphate stay in company hands, so they barely show here. {site}
Lithium
Kaustinen: drilling for batteries
Colour the holes by target and switch to lithium. In the Kaustinen area of western Finland, GTK drilled lithium pegmatites such as Syväjärvi and Rapasaari between 2004 and 2011, before a battery metals boom made them valuable.
These spodumene bodies are now the Keliber project, which mines them and turns the concentrate into lithium hydroxide at a refinery in Kokkola. {site}
The atomic years
Hunting uranium
Switch the target colour to uranium. From the 1950s to the 1980s Sweden searched for its own nuclear fuel. AB Atomenergi drilled the alum shale at Ranstad, between Falköping and Skövde, and mined it from 1965 to 1969, but the low-grade shale never paid.
Later SGU, LKAB and the nuclear fuel company SKBF drilled uranium finds in Norrbotten and Jämtland. No large uranium mine followed, and the dense clusters at Pleutajokk, Kvarnån and Lilljuthatten are what is left of that search.
How to read this data
What the dots are, and what they are not
Each dot is a drill collar from the GTK and SGU registers, drawn with its published dip, direction and length. These registers carry no assays or commodity, so the colours show the year and a target commodity taken from the nearest deposit in the GTK or SGU mineral deposit databases (within 3 km in Finland, 2 km in Sweden). About 9,300 Swedish holes have no coordinates and are left out.
The holes belong to earlier explorers and miners, often state companies that no longer exist. Today's mine owners hold much more drilling that is not public. Contains data from the Geological Survey of Finland (GTK), CC BY 4.0, and the Geological Survey of Sweden (SGU), CC0.
