MineGuessr – Siilinjärvi, Finland: Apatite–Phosphate Open-Pit Mine in Central Finland

MineGuessr Advent Calendar 2025 – Door 22

Siilinjärvi is one of the mines featured in our 2025 MineGuessr mining advent calendar. Each December day, we reveal a new mining satellite timelapse and invite you to guess the mine from satellite imagery of mines across the Nordics and Europe.

On this page, we provide a concise, professional overview of Siilinjärvi – its location, geology, operational history and role in the raw materials value chain. The satellite timelapse highlights how an Archean carbonatite in central Finland has been turned into the European Union’s only operating phosphate mine, supporting raw materials education around fertiliser nutrients and food security.

Aerial view of the Siilinjärvi apatite–phosphate open-pit mine, concentrator and phosphogypsum stacks near Kuopio, Finland

Overview & location

Siilinjärvi is a long-life apatite–phosphate open-pit mine located near the city of Kuopio in North Savo, central Finland. The deposit sits within the Siilinjärvi carbonatite complex, a steeply dipping, Archean intrusive body that stands out geologically and visually in the Finnish bedrock.

The mine started production in 1979 and has been in continuous open-pit operation ever since. Today it is run by Yara Suomi Oy as part of a vertically integrated fertiliser site that includes a concentrator, phosphoric acid plant, fertiliser production and associated infrastructure.

Siilinjärvi is often described as:

Western Europe’s only phosphate mine and, currently, the only operating phosphate mine in the European Union.
One of Finland’s largest open pits by amount of quarried rock.
A key supplier of phosphate rock for Yara’s European fertiliser production.

Where in the world is Siilinjärvi?

Country & region: North Savo, central Finland, close to Kuopio and the town of Siilinjärvi.
Geological setting: Within the Archean Iisalmi granite–gneiss terrain of the Fennoscandian Shield.
Mine layout: Two open pits – the main Särkijärvi pit (approx. 250 m deep) and the smaller Saarinen satellite pit a few kilometres to the north.
Industrial site: Integrated concentrator, phosphoric acid plant, fertiliser production units and large tailings and phosphogypsum stacks adjacent to the pits.

Geology & deposit type

Siilinjärvi is a textbook example of an apatite-bearing carbonatite complex.

Key geological features:

The deposit is hosted by a 16 km long, steeply dipping Archean carbonatite–glimmerite intrusion – one of the oldest known carbonatites on Earth (~2.61 Ga).
Ore-bearing rocks form a series of glimmerite–carbonatite varieties containing fluorapatite, phlogopite, carbonates (calcite, dolomite) and amphiboles, with accessory magnetite and zircon.
Almost all of the glimmerite–carbonatite series rocks are considered ore-grade, with an average in situ grade around 4 wt-% P₂O₅.
Mineralisation is broadly continuous along strike and depth within the intrusion, lending itself to large-scale open-pit mining.

For MineGuessr, Siilinjärvi represents the fertiliser-grade phosphate end of the raw materials spectrum – very different from copper, gold or iron ore, yet equally critical for the functioning of modern societies.

What the mining satellite timelapse shows

The mining satellite timelapse for Siilinjärvi (1984–2022) compresses almost the entire history of the open pit into a short video. Because the mine started in 1979, the earliest frames already show an active operation – but the scale and footprint change dramatically over time.

1980s – early Särkijärvi pit and initial tailings

Mining is concentrated in the southern Särkijärvi pit, with relatively modest depth and footprint compared to today.
An on-site concentrator produces apatite concentrate for phosphoric acid and fertiliser production.

On the timelapse:

You see a single, developing open pit in a largely forested landscape.
A small but recognisable tailings pond appears adjacent to the plant, with some light-toned areas starting to form.

1990s–2000s – deepening Särkijärvi and growing tailings

Production ramps up to the multi-million-tonne-per-year range, with Siilinjärvi establishing itself as a major phosphate source for European fertiliser manufacture.
By the mid-2000s, hundreds of millions of tonnes of rock have been mined; ore reserves are still substantial and planning assumes continued long-term operation.

In satellite imagery:

The main pit becomes deeper and more elongated, with new pushbacks and wider benches.
The tailings and phosphogypsum areas expand significantly, forming pale, almost white surfaces that contrast strongly with the surrounding forest and farmland.

2010s – Saarinen satellite pit and larger footprint

Mining extends to the Saarinen satellite pit north of Särkijärvi, while Särkijärvi continues to deepen.
Annual ore production stabilises around ~11 Mt of ore per year, with apatite concentrate produced for on-site phosphoric acid and external Yara plants.
By 2016, more than 400 Mt of rock have been mined; ore reserves are on the order of 200 Mt.

On the timelapse:

A second open pit appears to the north, giving Siilinjärvi a two-pit pattern that is easy to spot.
The tailings pond and phosphogypsum stacks keep growing, creating a large, light-coloured industrial landscape east of the pits.

2020s – critical EU phosphate and phosphogypsum management

Siilinjärvi’s role in European phosphate supply becomes even more visible as Yara increases sourcing from its own mine in response to geopolitical shocks in imported phosphate rock.
Environmental management focuses on phosphogypsum stacks, water quality and tailings stability, with monitoring and best practices documented at the EU and Baltic Sea level.

In the latest frames:

The pits show incremental deepening, but the most striking visual features are the large pale tailings and gypsum areas – almost like an industrial “white plateau” next to the pits.
These light-toned deposits are a key clue for MineGuessr players trying to distinguish Siilinjärvi from other open pits in the calendar.

Mining method & processing – how the ore moves

Siilinjärvi is a classic open-pit truck–shovel operation with integrated processing:

Open-pit mining: Drill-and-blast benches in glimmerite–carbonatite ore; ore and waste are loaded by hydraulic excavators and wheel loaders into haul trucks.
Beneficiation: Crushing, grinding and flotation produce an apatite concentrate with P₂O₅ contents around 36–37 wt-%.
On-site processing: Most of the concentrate is processed in the Siilinjärvi phosphoric acid plant using sulphuric acid, generating phosphoric acid and phosphogypsum.
By-products: Mica and calcite concentrates are produced in smaller quantities.
Logistics: Fertilisers and intermediates are shipped from Siilinjärvi and Yara’s other plants to European and global markets.

Role in the raw materials value chain & energy transition

Siilinjärvi is a critical node in Europe’s fertiliser and food value chain:

As the EU’s only operating phosphate mine, it provides domestic phosphate rock for fertiliser production.
This supports European food security, especially when import routes from Russia or other suppliers are disrupted.
Phosphate from Siilinjärvi is turned into fertilisers used across the region, underpinning yields for grains, oilseeds and other crops.

From an energy transition perspective, the mine illustrates how securing nutrient raw materials is part of the same conversation as securing metals for batteries and grids. Low-carbon agriculture, bio-based materials and resilient food systems all start with access to reliable, responsibly sourced fertiliser inputs.

At the same time, Siilinjärvi and its phosphogypsum stacks are used in international case studies on tailings and residue management, showing how long-lived operations address legacy and future environmental risks.

What to look for in the MineGuessr timelapse

As a MineGuessr player, see if you can spot:

The early development of the Särkijärvi pit in the 1980s, before the second pit appears.
The emergence of the Saarinen satellite pit to the north and how both pits deepen over time.
The growth of the tailings pond and phosphogypsum stacks – a large, pale industrial landscape that is very distinctive from space.
The way Siilinjärvi’s footprint differs from metal mines: more light-coloured residue surfaces relative to the dark rock of the pits and waste dumps.

MineGuessr perspective – why this mine was included

We selected Siilinjärvi for the MineGuessr mining advent calendar because it:

Is the only operating phosphate mine in the EU and a key pillar of European fertiliser supply.
Provides a clear example of an apatite-bearing carbonatite mined at large open-pit scale.
Shows a distinctive visual signature in satellite imagery, thanks to twin pits and large, pale phosphogypsum and tailings deposits.

In our GeoGuessr-style mine guessing game, Siilinjärvi helps spark conversations about fertiliser raw materials, carbonatite geology, tailings management and how food security is tied to responsible mining.

Throughout December, keep opening a new door every day and explore all 24 mines featured this year on the main MineGuessr mining advent calendar page.

Day 1 - Aitik (Sweden, copper-gold open pit)
A large, low-grade copper operation south of Gällivare
👉 Open Door 1 - Aitik
Day 2 - Björkdal (Sweden, gold)
Gold mine near Skellefteå, combining open-pit and underground mining.
👉 Open Door 2 - Björkdal
Day 3 - Kemi (Finland, chrome)
Chrome mine in northern Finland, Europe’s only chromite operation.
👉 Open Door 3 - Kemi
Day 4 - Ørtfjell (Norway, iron ore)
Iron ore mine in Norway’s Dunderland Valley, evolving from large open pits to underground mining.
👉 Open Door 4 - Ørtfjell
Day 5 - Trimouns (France, talc)
World’s largest working talc quarry high in the French Pyrenees above Luzenac.
👉 Open Door 5 - Trimouns
Day 6 - Skouries (Greece, copper-gold porphyry)
High-grade copper–gold porphyry project in the forests of Halkidiki, still under construction.
👉 Open Door 6 - Skouries
Day 7 - Las Cruces (Spain, copper)
High-grade hydromet copper mine in the Iberian Pyrite Belt north-west of Seville.
👉 Open Door 7 - Las Cruces
Day 8 - Assarel–Medet (Bulgaria, copper)
Twin porphyry copper open pits in the Panagyurishte district, from Europe’s former largest open-pit copper mine at Medet to today’s modern Assarel operation.
👉 Open Door 8 - Assarel–Medet
Day 9 - Glomel (France, andalusite)
World-class andalusite open-pit quarry in Brittany’s Montagnes Noires, supplying refractory minerals for Europe’s steel, foundry, cement and glass industries.
👉 Open Door 9 - Glomel
Day 10 - Parnassos–Ghiona (Greece, bauxite)
Karst-type bauxite mines in the Parnassos–Ghiona mountains, a historic alumina feedstock district supplying Greece’s aluminium industry.
👉 Open Door 10 - Parnassos–Ghiona
Day 11 - Kittilä (Finland, gold)
Europe’s largest primary gold mine at the Suurikuusikko orogenic gold deposit north of the Arctic Circle.
👉 Open Door 11 - Kittilä
Day 12 - Oltenia Energy Complex (Romania, lignite)
Cluster of large open-pit lignite mines and mine-mouth power plants in Gorj County, now at the centre of Romania’s coal phase-out and just transition plans.
👉 Open Door 12 - Oltenia Energy Complex
Day 13 - Cornwall china clay (UK)
Historic Imerys china clay pits near St Austell, where bright white kaolin benches and tips reshape “Clay Country” over decades of mining and restoration.
👉 Open Door 13 - Cornwall china clay
Day 14 - Aggeria–Agia Irini (Greece, bentonite)
Overlapping bentonite open pits on the volcanic island of Milos, anchoring one of Europe’s key industrial minerals districts.
👉 Open Door 14 - Aggeria–Agia Irini
Day 15 - Skouriotissa (Cyprus, copper & hydromet)
Ancient copper mining district in the Troodos ophiolite, now a hydrometallurgical hub processing copper, gold and battery-metal feed.
👉 Open Door 15 - Skouriotissa
Day 16 - Tunstead (UK, limestone & cement)
The UK’s largest limestone quarry near Buxton, feeding an integrated lime and cement works with long-term restoration and biodiversity plans.
👉 Open Door 16 - Tunstead
Day 17 - Narva (Estonia, oil shale)
Large open-pit oil shale mine in Ida-Viru County, supplying the Narva power plants and reshaping the landscape with strip mining and reclamation.
👉 Open Door 17 - Narva
Day 18 - Sydvaranger (Norway, iron ore)
Arctic banded iron formation at Bjørnevatn near Kirkenes, evolving toward DR-grade magnetite for Europe’s green steel transition.
👉 Open Door 18 - Sydvaranger
Day 19 - Kevitsa (Finland, nickel–copper–PGE)
Multimetal open-pit mine in Finnish Lapland, combining Ni–Cu–PGE production with trolley-assisted haulage for lower-emission mining.
👉 Open Door 19 - Kevitsa
Day 20 - Styrian Erzberg (Austria, iron ore)
Terraced “pyramid” open-pit iron ore mine at Eisenerz, turning 12 Mt of rock into ~3 Mt of ore each year for Austria’s steel industry.
👉 Open Door 20 - Styrian Erzberg
Day 21 - Minas de Alquife (Spain, iron ore)
Europe’s largest open-pit iron ore mine in Granada, restarting in 2020 after two decades of closure to supply high-grade ore to European steelmakers.
👉 Open Door 21 - Minas de Alquife
Day 23 - Tellnes (Norway, ilmenite/titanium)
World-class ilmenite open pit in the Rogaland Anorthosite Province, supplying TiO₂ pigment feedstock from one of Europe’s largest titanium deposits.
👉 Open Door 23 - Tellnes
Day 24 - Elatsite (Bulgaria, copper–gold porphyry)
High-altitude porphyry copper–gold open pit in Bulgaria’s Srednogorie zone, with ore conveyed under the Balkan Mountains to a separate flotation–tailings complex.
👉 Open Door 24 - Elatsite

About Gosselin Mining

At Gosselin Mining, we work with long-life open pits and critical raw material value chains like Siilinjärvi: carbonatite and industrial mineral deposits, bulk mining, tailings and residue strategies, and projects where fertiliser supply, ESG performance and regulatory expectations all intersect.

Stress-test your life-of-mine plan and closure strategy for phosphate or other industrial mineral operations
Evaluate options for tailings, residue and by-product management, including phosphogypsum or similar streams
Benchmark your ESG profile and raw-materials positioning against Nordic and European peers

…you’re very welcome to book a meeting with us.