BluMelt Mineral Consulting Limited

Bentonite in Europe

Executive summary

In 2025, the EU-27 imported 1.02 million tonnes of bentonite worth €175.8 million from outside the bloc under customs code CN 25081000. Türkiye supplied 72% of that tonnage.¹ The EU also has its own bentonite mines, including in Greece. For buyers, the question is how much of the grade they use an alternative supplier can deliver at short notice.

• Grade availability is driven by geology and processing: A supplier's ability to deliver a specific grade depends on the mineralogy and variability of the mine feed, the plant's processing and activation route, and exact end-use performance. The Milos deposit in Greece illustrates how clay quality can vary significantly within a single mining district.
• Supplier switching depends on strict application rules: Substitution requirements vary widely by industry. A foundry requires a bentonite binder that performs reliably in its specific moulding sand system, whereas Ireland's Lough Ree landfill capping specification enforces separate acceptance criteria for both the raw clay and the finished geosynthetic liner.
• Customs data show where imports come from: CN 25081000 records bentonite imports by origin. It does not distinguish grades by end-use performance, and some activated products are classified under other codes. A buyer's approved supplier list is needed to assess which sources could serve as alternatives.
• Disruption planning requires technical verification: To accurately gauge supply risk, buyers must verify that an alternative material meets their exact specifications and that the supplier's plant can consistently deliver the required volume.

Scope and methodology

This assessment covers the EU-27 bentonite market and the countries that supply it. It draws on published studies of bentonite deposits and processing, mine production statistics and annual trade data from Eurostat. Production and trade figures are reported with their reference years. Two examples show what buyers look for in different applications: bentonite binders for foundry moulding sand, and geosynthetic clay liners for landfill capping.

Deposit geology and resource quality

Bentonite is an industrial clay rock composed mainly of smectite, usually montmorillonite, with many bentonite deposits forming as in-situ beds of altered volcanic ash or other glass-rich volcanic material. The commercial term also covers some swelling clays formed through other processes, including weathering and hydrothermal alteration. How the deposit formed helps explain how far the clay beds extend and where impurities are likely to occur. Even a relatively uniform ash-derived bed can contain thin layers of sand, silt or gypsum. If those layers are mined along with the clay, a sample taken from the cleanest part of the bed can overstate the quality of the material that will reach the processing plant.^2,3

Smectite layers carry a negative charge balanced by exchangeable cations such as sodium, calcium and magnesium. The mix of these cations affects how much water enters between the layers and how the clay swells and forms a gel. Sodium-dominant bentonite generally swells more than calcium-dominant bentonite, a useful property in drilling fluids and seals. Foundries, however, place different demands on the clay. Calcium bentonite can improve the strength of a mould while it is moist, while sodium bentonite can contribute to its strength after drying. To assess a deposit for a particular market, X-ray diffraction identifies the smectite and other minerals present. Measurements of exchangeable cations show which ions dominate, and cation exchange capacity indicates how much charge the clay can exchange. These results help explain how the clay is likely to behave. Tests on representative material establish whether it meets the performance requirements for the intended use.²

The bentonite deposits on Milos, Greece, show how clay composition can vary within a single mining district. Pusch³ describes smectite-rich clays containing quartz and mica at Agrilies, and clays with less smectite and appreciable amounts of silica minerals at Ano Komia. This variation affects how much bentonite the district can supply for a particular product. The operator needs to establish which beds can be mined separately, how much usable clay may be lost when thin layers of other material are removed, and whether stockpiles can be blended to maintain a consistent feed as mining moves from one bed to another. These factors determine how much of the district's total resource can supply a given grade.²

Mining, processing and commercial grades

Bentonite is typically mined from open pits after the overburden is removed. Where clay composition varies across the pit, operators can stockpile material separately and blend it to give the plant a more consistent feed. Processing typically involves crushing, controlled drying and grinding to the particle size required for the finished product. Some plants also remove sand or other impurities. When the target product requires greater swelling, processors can treat calcium-rich clay with soda ash. This treatment, known as sodium activation, replaces some of the exchangeable calcium with sodium. The resulting increase in swelling depends on the clay and the treatment conditions. Laboratory and pilot-scale trials should therefore cover the range of clay compositions the plant is expected to receive and test whether the finished product consistently meets its specification.^4,5

The supply chain should be assessed from saleable dry tonnes and measured batch performance. A plant can have adequate nominal capacity and still struggle to supply a given grade if the mine plan yields too little suitable feed, drying limits throughput or the blend varies beyond the customer's tolerance. As such, suppliers should be compared using the same performance test and moisture basis, checking how each product behaves in the buyer's own process. That is the point at which a geological resource and processing route can be translated into a credible supply option.

European supply and trade

The EU has a substantial bentonite mining base, while Türkiye is its largest external source under CN 25081000. The British Geological Survey (BGS) records 1.03 million tonnes of bentonite for Greece in 2024, 329,000 tonnes for Italy, 319,000 tonnes for Slovakia and 260,000 tonnes for Germany. BGS reports 731,000 tonnes of bentonite sales for Bulgaria, while the US Geological Survey estimates Bulgarian bentonite production at 52,000 tonnes for the same year. The two sources report different measures, so Bulgaria's sales figure is excluded from the production comparison here. BGS records 2.53 million tonnes of production for Türkiye in 2024, up from 1.66 million tonnes in 2020.^6,7

Table 1. EU-27 external bentonite trade, 2023–2025

Year	External imports (kt)	Import value (€m)	External exports (kt)	Export value (€m)	Imports from Türkiye (kt)	Türkiye share of import tonnage
2023	891.6	166.1	244.1	48.8	720.0	81%
2024	986.7	171.9	261.6	53.2	746.0	76%
2025	1,020.7	175.8	161.9	46.5	734.4	72%

Extra-EU imports under this code reached 1.02 million tonnes in 2025, the highest of the three years shown. Türkiye's share fell from 81% in 2023 to 72% in 2025, while its shipments stayed between roughly 720,000 and 746,000 tonnes a year. Imports from India nearly doubled, from 46,531 tonnes in 2023 to 92,008 tonnes in 2025. Morocco supplied 44,474 tonnes in 2025 and Georgia 40,493 tonnes. Türkiye still accounted for 65% of the EU's €175.8 million external import bill. Net external imports rose from 725,075 tonnes in 2024 to 858,788 tonnes in 2025, driven chiefly by lower export volumes. Member states separately reported 1.23 million tonnes of arrivals from other EU members in 2025. Those flows describe circulation within the EU and can include redistributed material. They should be kept separate when reading the external balance.⁸

Industrial applications and qualification requirements

A deposit's smectite content and exchangeable cations help identify potential markets. Commercial qualification follows a different sequence. A processor must repeatedly deliver a defined product after selection, activation or blending where required, drying and sizing. The buyer then evaluates that product in a particular process or finished assembly. Foundry sand and geosynthetic clay liners illustrate how this distinction changes which deposits, processors and suppliers can serve a market.

Foundry green-sand binders

In green-sand moulding, hydrated bentonite coats and binds the sand grains. The European Commission's technical reference for smitheries and foundries describes extensive use of soda-activated calcium bentonites in European ferrous foundries. Soda ash treatment allows calcium-rich feed to produce a binder with properties approaching those of natural sodium bentonite. The reference identifies high dry strength, tolerance to variation in moisture, and resistance to thermal degradation as useful attributes of natural sodium material. It also describes applications in higher-value steel castings and blends with activated calcium material. LKAB Minerals reports supplying both naturally occurring sodium and activated calcium bentonite raw materials from US and Greek origins. The disclosures identify commercial product routes and reported sources. Qualification at an individual foundry still depends on the sand system and casting conditions.^9,10

The relevant comparison is performance at a given dose in the foundry's sand blend, moisture range and thermal cycle. A substitution trial would compare mould strength and workability, then check how much active binder remains after casting and how much fresh material the reclaimed sand requires. A cheaper delivered tonne can increase cost per acceptable casting if the foundry has to raise binder dosage or compensate for faster loss of activity during sand reuse. For supply assurance, the evidence to request is representative lot data and results from trials in the customer's sand system. Where activation is part of the route, the continuity of soda ash supply and the processor's ability to keep activation and blending consistent also matter.

Geosynthetic clay liners at Lough Ree

The 2021 engineering works proposal for permanent capping at Ireland's Lough Ree Power Ash Disposal Facility specifies a geosynthetic clay liner containing granular natural sodium bentonite. The liner must contain at least 3.0 kg of clay per square metre at 12% moisture, and the clay must contain approximately 90% montmorillonite, measured by X-ray diffraction. The proposal calls for independent test evidence before orders are placed and checks on components when they arrive at the factory. Finished rolls are checked for bentonite mass per unit area and mechanical strength, tracked by lot and roll number, and protected from premature hydration during handling and storage.¹¹

Qualifying an alternative supplier involves checking both the clay and the finished liner. ASTM D5890¹² measures how much the clay swells in reagent water and applies to clays without polymer additives. If the liner will be exposed to a liquid that could affect its performance, ASTM D6766¹³ can be used to measure the finished liner's hydraulic conductivity with that liquid. When assessing an alternative supplier, check which clay goes into the roll and whether the test conditions and manufacturing records support its use on the project.

Other end markets

Different uses call for different properties. Drilling fluid buyers check how the fluid flows and how much liquid it loses by filtration. API Spec 13A distinguishes between bentonite, untreated bentonite and OCMA-grade bentonite.¹⁴ Iron ore pellet producers check how well bentonite binds their ore into pellets, while pet litter producers look for absorbency and ease of handling.¹⁵ Total bentonite tonnage gives an indication of market size. Before switching suppliers, a buyer needs to confirm the grade and form in which the product is delivered, check how it was tested and verify that it meets their requirements.

EU regulatory context

Mine development and extractive waste: The Environmental Impact Assessment Directive places quarry and open-cast mining projects exceeding 25 hectares in Annex I. Quarry and open-cast mining projects that do not exceed 25 hectares fall within the Annex II screening framework, with determinations made under Article 4 and national implementation. The Extractive Waste Directive covers waste arising from extraction, treatment and storage of mineral resources within its scope. Its requirements depend in part on the waste characteristics and the facility category. For supply planning, the relevant evidence includes the approved operating footprint, the status of any extension and the extractive waste arrangements.^16,17

Processing and EU market placement: REACH Annex V, entry 7 provides an exemption from registration for naturally occurring minerals meeting the conditions in the entry, including that they are not chemically modified. Articles 3(39) and 3(40) define the relevant terms. Drying, grinding, soda activation, acid activation and organophilic treatment should be assessed against the actual manufacturing route and substance identity. Classification and labelling under CLP require a separate determination for the relevant substance or mixture.^18,19

Supply risks and conclusions

Türkiye supplied 72% of the EU's extra-EU bentonite import tonnage recorded under CN 25081000 in 2025. Its share fell from 81% in 2023 as imports from other origins grew, while Turkish volumes stayed broadly stable. For buyers assessing a possible disruption, the table below sets out what to verify at the mine, at the processing plant and in their own operation.

Table 2. Assessment areas and technical evidence for supplier qualification

Assessment area	Evidence required
How much suitable clay can the mine supply?	Samples from the beds scheduled for mining and from stockpiles, evidence of what can be mined separately or blended, and an estimate of saleable dry tonnes for the required grade
Can the plant make and deliver that grade consistently?	Actual throughput and batch results for the grade, any reliance on a particular activation or milling facility, and the packaging, freight route, lead time and delivered cost per dry tonne.
Will it work in the customer's process?	Laboratory results using comparable test methods, trials under normal operating conditions, and evidence that successive batches perform consistently. Allow for the time needed to test and approve the product.

For a buyer that needs a specific natural sodium grade or an acid-activated product, the search starts with deposits and plants that can supply it. Even two approved suppliers can be exposed to the same disruption if they rely on the same processing plant or freight route.

For an investor, tracing the material from the deposit to the finished product helps establish how much can realistically be mined, processed and sold into the target market. For a buyer, the result is an estimate of how much replacement material can be delivered within the time available.