MineGuessr – Glomel, France: Andalusite Open-Pit Mine in Brittany’s Montagnes Noires

MineGuessr Advent Calendar 2025 – Door 9

Glomel 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 Europe and the Nordics.

On this page, we provide a concise, professional overview of the Glomel andalusite mine – its location, geology, operational history and role in the raw materials value chain. The satellite timelapse helps illustrate how this open-pit industrial minerals operation has evolved since the 1970s and supports raw materials education for anyone interested in how strategic refractory minerals are produced.

Aerial view of the Glomel andalusite open-pit mine in Brittany’s Montagnes Noires

Overview & location

From space, Glomel appears as a bright, terraced open pit with pale benches and grey waste piles set in the green landscape of inland Brittany. Over almost five decades, the timelapse captures the transition from a single pit and small plant to a multi-pit quarry with on-site processing, water management infrastructure and large overburden dumps.

The andalusite mine is located at Guerphalès on the commune of Glomel, Côtes-d’Armor, Brittany, France, on the northern flank of the Montagnes Noires. It is operated by Imerys and is recognised as a world-class andalusite deposit and the only producing andalusite mine in Europe.

Andalusite has been mined at Glomel since 1970.
The site covers around 250 hectares and currently employs roughly 110 people.
Each year, about 1.2 Mt of ore are mined to produce approximately 65,000 t of refined andalusite, representing roughly 20–25% of global production.

This makes Glomel not only a key industrial site for Brittany, but also a strategic node in the global supply of high-grade alumino-silicate for refractories.

Geology & deposit type

Glomel is an andalusite-bearing metamorphic deposit hosted in schists of the Montagnes Noires. The local deposit, often referred to as Guerphalès or “Kerphalès”, is notable for having some of the highest andalusite grades in the world.

Key geological points:

The ore occurs in andalusite-rich schists formed during regional metamorphism of aluminous sediments.
Andalusite (Al₂SiO₅) is valued for its very high temperature resistance and excellent thermal shock behaviour.
After processing, Glomel andalusite is sold into refractory bricks and castables used in steel, foundry, cement and glass industries across Europe and beyond.

For MineGuessr, Glomel represents the industrial minerals / refractory raw materials side of the portfolio, contrasting with the copper, gold, iron ore and talc operations featured on other doors.

What the mining satellite timelapse shows

The mining satellite timelapse for Glomel (1984–2022) compresses decades of quarry development into a few seconds. It neatly tracks the life of a large European industrial minerals site through successive pits and increasing production.

1970s–1980s – first pits and plant construction

Start-up: The first pit opens in 1970 alongside the original Damrec refractory materials plant.
A second pit is developed in the mid-1980s to sustain production as demand for andalusite grows.

What you see from space:

- A small, light-coloured excavation in the hillside surrounded by forest and farmland.
- The initial plant area and settling ponds appearing next to the pit.
- First overburden and waste-rock dumps building up around the operation.

1990s–2000s – third pit and footprint expansion

In 1998, the first pit is closed and a third pit begins production to maintain long-term supply.
On the ground, Imerys progressively upgrades crushing, screening and separation circuits to increase product quality and yield.

In the timelapse:

The original excavation stabilises, while a new active pit opens nearby.
Waste dumps expand and are reshaped, forming elongated pale-grey ridges.
Process water ponds and sediment basins become more prominent and structured.

2010s–early 2020s – higher output, environmental scrutiny

Annual production reaches around 65,000 t of refined andalusite, approximately a quarter of world output, with ore extraction around 1.2 Mt per year.
Glomel is formally recognised as the only andalusite mine in Europe and a strategic industrial minerals site for the EU.
At the same time, the site faces increasing environmental and community scrutiny, particularly around water quality in nearby streams and wetlands.

In the timelapse:

You see a mature pit complex with large, pale benches and engineered slopes.
Waste-rock storage areas and tailings / water management infrastructure become clearer and more extensive.
The overall footprint is substantial but remains constrained within a defined industrial envelope.

Mid-2020s – fourth pit and water treatment investments

Imerys secures permits for a fourth extraction pit to extend the mine life into the 2040s.
A new water treatment plant is commissioned to reduce manganese and other elements in discharge water and comply with tighter environmental regulations.

From a MineGuessr perspective, these later frames show a large European open pit adapting to modern ESG expectations: incremental expansion, new water management infrastructure and a gradual re-shaping of dumps and ponds rather than “greenfield” disturbance.

Mining method & processing – how the ore moves

Glomel is a classic open-pit drill-and-blast quarry with on-site beneficiation of industrial minerals:

Mining: Andalusite-bearing schists are drilled, blasted and loaded with excavators into haul trucks, working in multiple pits.
Crushing & screening: Run-of-mine ore is crushed and screened to liberate andalusite grains.
Concentration: A combination of magnetic and electrostatic separation is used to separate andalusite from other silicate and oxide minerals.
Final products: The concentrate is milled into powders and granules tailored for refractory brick and castable formulations.
Water circuit: Process water is largely recycled in a closed circuit and treated prior to discharge to the environment.

Role in the raw materials value chain and energy transition

Glomel’s output feeds into the refractory supply chain, which underpins a wide range of high-temperature industrial processes:

Steel & foundry: Linings for blast furnaces, ladles and foundry equipment.
Cement & lime: Refractory bricks and castables in rotary kilns and coolers.
Glass & ceramics: Kilns, tanks and other furnace components.

Although andalusite is not a battery metal, its role is tightly coupled to the energy transition: steel, cement and glass are all essential to power grids, wind turbines, solar infrastructure and transport electrification. Secure European supply of high-performance refractories supports resilient low-carbon value chains.

What to look for in the MineGuessr timelapse

As a MineGuessr player, can you spot:

The sequence of pits opening and closing over time (early pits stabilising as newer pits become active).
The growth and reshaping of waste dumps and pale benches as more andalusite-bearing schist is mined.
Changes in water management structures – ponds, channels and treatment basins – as environmental requirements tighten.
The contrast between the bright mine footprint and the surrounding green forests and fields of inland Brittany.

MineGuessr perspective – why this mine was included

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

Showcases a world-class industrial minerals deposit – the only producing andalusite mine in Europe and one of the highest-grade deposits worldwide.
Provides a clear visual example of how a large open-pit quarry evolves over decades in a temperate, rural landscape.
Illustrates strategic questions around European raw materials security, industrial policy and environmental performance for refractory minerals.

In our GeoGuessr-style mine guessing game, Glomel helps spark conversations about industrial minerals, refractories and the link between “invisible” quarries and everyday high-temperature industries.

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 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 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 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

About Gosselin Mining

At Gosselin Mining, we work with exactly the kind of long-life operations that Glomel represents: industrial minerals quarries and strategic raw materials assets where value comes from geology, mine design, permitting strategy and ESG-driven process optimisation. If you need help to:

Assess the life-of-mine potential of an industrial minerals or refractory raw materials project
Optimise open-pit design, waste management and water circuits for complex near-surface deposits
Benchmark your operation against European raw materials and ESG expectations

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