MineGuessr – Assarel–Medet, Bulgaria: Twin Porphyry Copper Open Pits in Central Sredna Gora

Overview & location

The Assarel–Medet Mining and Processing Complex lies in the Panagyurishte ore district of central Bulgaria, within the Sashtinska Sredna Gora Mountains. The Assarel pit and concentrator are located about 11 km northwest of the town of Panagyurishte and roughly 90 km east of Sofia, at around 1,000 m elevation.

The complex brings together two related porphyry copper deposits:

• Medet open pit – discovered in the late 1950s, built in the early 1960s and officially inaugurated in 1964. At that time it was the largest open-pit copper mine in Europe and the third largest in the world, with a design capacity of 8 Mt/y of ore.
• Assarel open pit – a separate porphyry copper deposit about 12 km away, developed from the mid-1970s and commissioned with its own concentrator in 1989.

Today, Assarel–Medet JSC is Bulgaria’s leading open-pit copper mining and processing company, processing roughly 13–14.5 million tonnes of ore annually and supplying around half of Bulgaria’s copper ore production.

Geology & deposit type

Both Assarel and Medet are Late Cretaceous porphyry copper deposits in the Central Srednogorie zone of the Apuseni–Banat–Timok–Srednogorie belt, part of the broader Tethyan copper province.

Key geological features:

• Deposit type: Hydrothermal porphyry Cu system with stockwork and disseminated mineralisation.
• Main ore minerals at Assarel: chalcocite (chalcosine), pyrite, chalcopyrite, bornite and covellite, with an average copper grade of about 0.45% Cu.
• Precious metals: Studies show that Assarel carries gold, silver and platinum-group elements associated with sulphides and late-stage veins, making it one of the larger precious-metal–bearing porphyry systems in Europe.
• Assarel–Medet system: Geochronology and petrology indicate that Medet and Assarel were formed within a short-lived (<1 Ma) magmatic–hydrothermal system, effectively a twin porphyry cluster rather than isolated deposits.

For MineGuessr, Assarel–Medet represents the porphyry copper cluster end of the calendar – a nice contrast to single orebodies like Aitik or Skouries.

What the mining satellite timelapse shows

The mining satellite timelapse for Assarel–Medet (1984–2022) is almost a textbook case of how two neighbouring porphyry copper pits can follow different life cycles over forty years.

1. 1980s – Medet at full scale, Assarel emerging

• By the mid-1980s, Medet is a very large, mature open pit with extensive dumps and a concentrator plant, operating at its full design capacity of 8 Mt/y of ore (achieved in 1972).
• Assarel is still in early stages: experimental mining began in 1976 and ore was processed through the Medet facilities; the dedicated Assarel concentrator only comes on stream in 1989.

From space: you see a dominant, wide Medet pit with large waste dumps and a tailings impoundment, while Assarel appears as a smaller, growing excavation to the southwest.

2. 1990s – Medet closure, Assarel expansion

• In accordance with the mine plan, Medet begins to reduce output from 1984 and ceases production in early 1994.
• A rehabilitation programme is launched for the Medet pit, dumps and hydrographic network, with long-term monitoring of soil and water as part of a 15-year restoration plan.
• Assarel, by contrast, ramps up: full design capacity is reached in the mid-1990s and it becomes the core of the Assarel–Medet operation.

In the timelapse: Medet’s pit stops deepening and gradually shows more water and vegetation on benches and dumps, while the Assarel pit continues to widen and the tailings pond and dumps expand.

3. 2000s – modernisation and higher throughputs at Assarel

• Assarel–Medet JSC undergoes major modernisation from 2004 onward, with around USD 100 million invested in new equipment, automation and environmental systems.
• The mine operates with annual ore throughputs on the order of 10–13 Mt/y, producing copper concentrate and cathode via a concentrator, SX–EW plant and dedicated return-water and leaching facilities.

In the imagery: you see the Assarel pit pushing back, waste dumps growing and the Lyuliakovitsa tailings facility gaining new cells and dam raises, while the Medet footprint stabilises.

4. 2010s–2020s – high-capacity porphyry and ongoing monitoring

• By the 2010s, Assarel–Medet processes around 13–14.5 Mt of ore per year, remaining Bulgaria’s largest open-pit copper operation and a major employer in Pazardzhik Province.
• Remote-sensing studies show that the active Assarel pit and tailings pond keep expanding modestly, while the reclaimed Medet area maintains a relatively stable footprint, with vegetation cover gradually increasing on backfilled and reshaped surfaces.
• The company operates environmental monitoring stations for air and water, with monthly bulletins and ISO-certified management systems, including ISO 14001.

From a MineGuessr perspective: the recent frames clearly show a dual story – one large pit in long-term care and maintenance, and another still actively moving rock and tailings.

Mining method & processing – how the ore moves

Assarel–Medet is operated as a large-scale truck–shovel open pit complex with integrated processing and SX–EW:

• Open-pit mining: Conventional drill–blast, load and haul on multiple 10–15 m benches, with 130 t haul trucks and large hydraulic excavators working several pushbacks at Assarel.
• Processing:
  • Crushing and grinding of ore at the Assarel concentrator.
  • Flotation to produce copper concentrate with payable by-products.
  • Hydrometallurgical facilities, including microbiological leaching and an SX–EW plant, to produce copper cathode in addition to concentrate.
• Waste and water management: Large external dumps and the Lyuliakovitsa tailings pond; active water-return systems and treatment, plus long-term monitoring of the closed Medet site to track rehabilitation and acid mine drainage risks.

Role in the raw materials value chain and energy transition

Assarel–Medet is one of the largest porphyry copper producers in south-eastern Europe, supplying copper concentrate and cathode into smelters such as Pirdop and into wider European value chains.

In the context of the energy transition, copper from Assarel–Medet supports:

• Electricity transmission and distribution – cables, transformers and substations for power grids.
• Electrification of transport – wiring, motors and charging infrastructure for EVs and rail.
• Renewables and industry – wind turbines, solar PV balance-of-plant equipment and industrial motors across the EU.

At the same time, the contrasting footprints of Medet (now closed and under rehabilitation) and Assarel (still active) make the complex a useful case study in life-of-mine planning, closure, reclamation and long-term environmental monitoring for porphyry copper districts in Europe.

What to look for in the MineGuessr timelapse

As a MineGuessr player, could you spot the following?

• The very large Medet pit dominating early frames, then gradually stabilising and showing more water and vegetation after closure in 1994.
• The continued expansion of the Assarel pit into the 2000s and 2010s, with new pushbacks and haul roads clearly visible.
• The growth of the Lyuliakovitsa tailings facility and associated water ponds as cumulative tonnage increases.
• The way two neighbouring porphyry copper deposits can follow different but complementary life cycles in the same district.

MineGuessr perspective – why this mine was included

We selected Assarel–Medet for the MineGuessr mining advent calendar because it:

• Highlights one of Europe’s classic porphyry copper clusters and the transition from an historic flagship pit (Medet) to a modern, upgraded operation (Assarel).
• Shows a clear life-of-mine contrast in the satellite timelapse – active expansion versus closure and rehabilitation within a single ore field.
• Represents a key part of south-eastern Europe’s copper supply, with strong links to regional smelters and downstream industrial consumers.

In our GeoGuessr-style mine guessing game, Assarel–Medet helps spark conversations about porphyry copper exploration, low-grade bulk mining, mine closure and landscape reclamation in an EU member state.

In 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 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 22 - Siilinjärvi (Finland, phosphate)
  EU’s only operating phosphate mine in central Finland, mining an Archean carbonatite for fertiliser-grade apatite and creating distinctive pale tailings and phosphogypsum stacks.
  👉 Open Door 22 - Siilinjärvi
• 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

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About Gosselin Mining

At Gosselin Mining, we work with exactly the kind of porphyry copper operations that Assarel–Medet represents: low- to medium-grade bulk deposits, large open pits, complex waste and water management, and long-term closure and rehabilitation plans.

If you’d like to:

• Stress-test a life-of-mine plan for a porphyry copper project or cluster
• Optimise cut-off strategies and pushback design in long-life open pits
• Benchmark your closure and reclamation concept using remote-sensing and ESG best practice

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

Further Reading and References

1. Assarel–Medet JSC (online). About Asarel – Medet. Available at: https://www.asarel.com/en/about/ (Accessed 7 December 2025).
2. Assarel–Medet JSC (online). Medet Mining and Processing Complex – History. Available at: https://www.asarel.com/en/about/history/medet-mining-and-processing-complex/ (Accessed 7 December 2025).
3. Wikipedia (online). Asarel Medet. Available at: https://en.wikipedia.org/wiki/Asarel_Medet (Accessed 7 December 2025).