This technical report presents the process design for a gold-copper concentrator at the Skouries Project on the Halkidiki Peninsula in northern Greece, based on metallurgical testwork and feasibility-level engineering.
Report context
This Technical Report on the Skouries Property was prepared by AMC Mining Consultants (Canada) Ltd. on behalf of Eldorado Gold Corporation, with an effective date of 22 January 2022. It is an update to the report with an effective date of 1 January 2018 and supports the annual statement of Mineral Resources and Mineral Reserves. The Property is located within the Kassandra Mines complex on the Halkidiki Peninsula of northern Greece, approximately 100 km east of Thessaloniki. Eldorado, through its 95% owned subsidiary Hellas Gold SA, owns the Property. The report covers a Feasibility Study for the Skouries Project.
Processing route
Process design basis
The processing facilities are designed to produce a gold-copper concentrate. For the first nine years of operation, ore will be extracted from both the open pit mine and underground mine for a total mill feed rate of 8.0 million tonnes per annum (Mtpa). From the tenth year until depletion of Mineral Reserves, the plant will process ore extracted from the underground mine at an average of around 6.5 Mtpa, tailing off in Years 19 and 20. During Years 10 to 14, previously stockpiled oxide ore will be re-handled to maintain mill feed at 8.0 Mtpa.
The plant will process copper-gold ore at a projected life-of-mine (LOM) average head grade of 0.50% copper and 0.77 g/t gold. Anticipated LOM average payable recoveries are 87% for copper and 81% for gold. The mill will produce a flotation concentrate containing an average of 26% copper and 27 g/t gold. Metallurgical tests have shown that the ore contains a small amount of palladium, which will be collected into the copper-gold concentrate during flotation.
Primary crushing and stockpile
The processing route begins with primary crushing followed by a crushed ore stockpile.
Grinding circuit and pebble crusher
The grinding circuit is designed as an SABC (semi-autogenous grinding, ball milling, and pebble crushing) configuration.
Flotation and regrinding
The flotation circuit includes flotation and regrinding stages. Gravity classification, secondary gravity classification, and gold room circuits have been designed, but installation has been deferred pending confirmation of the need for gravity concentration to meet designed overall gold recoveries.
Thickening
The process includes concentrate thickening and tailings thickening.
Concentrate filtering, storage, and loadout
Flotation concentrate will be filtered, stored, and loaded for transport.
Tailings filtration, conveying, and paste fill production
Tailings will be filtered and conveyed. A portion of filtered tailings will be used for paste backfill production.
Reagent preparation and services
The plant includes reagent preparation and general services areas.
Flotation reagents
The reagent system includes Sodium IsoPropyl Xanthate (SIPX) as a collector, Aeropromoter MX-5010 (or equivalent) as a promoter, frothers, and guar gum. A sulphidizer system and lime system are also included. A flocculant system is provided for thickening operations.
Process and fresh water management
Process water, utility water, firefighting water, and potable water systems are included in the plant design.
Key reported parameters
| Parameter | Unit | Design / Testwork Basis |
|---|---|---|
| Mill feed rate (Phase 1) | Mtpa | 8.0 (design) |
| Mill feed rate (Phase 2, Years 10-14) | Mtpa | 8.0 (design, including stockpiled oxide ore) |
| Mill feed rate (Phase 2, from Year 15) | Mtpa | 6.5 (design) |
| LOM average head grade, copper | % | 0.50 (design) |
| LOM average head grade, gold | g/t | 0.77 (design) |
| Payable copper recovery, LOM average | % | 87 (design) |
| Payable gold recovery, LOM average | % | 81 (design) |
| Concentrate grade, copper | % | 26 (design) |
| Concentrate grade, gold | g/t | 27 (design) |
| Grinding circuit type | , | SABC with pebble crushing (design) |
| Flash flotation | , | Testwork completed by Outotec (2007) |
| Gravity gold recovery | , | Testwork completed by Outotec (2007); supplementary testwork by FLS Knelson (2013) |
| Concentrate settling and filtration | , | Testwork completed by Outotec (2007) |
| Flotation concentrate testwork | , | Supplementary testwork by Wardell Armstrong (2015) |
| Selective flotation from pyrite-rich ore | , | Testwork by Solvay (2016) and Bureau Veritas Commodities Canada (2017) |
| Comminution circuit modelling | , | Orway Mineral Consultants review and circuit simulations (2014) |
| Original design basis testwork | , | Lakefield Research on core composites; Aker Kvaerner design (2007) |
Technical qualifications
The cost estimate is a feasibility-level estimate categorized as AACE Class 3. Direct costs were developed from a combination of budget quotes, material take-offs, existing contracts, Project-specific references, and historical benchmarks. Indirect and owners’ costs were estimated using a combination of existing commitments, calculated project requirements, and historical benchmarks.
Metallurgical testwork and studies were performed by Lakefield Research, Canada on composites selected from core samples of the major rock types, covering mineralogy, grinding and flotation. This testing was carried out to support the original 2007 design. Additional testwork was completed by Outotec in 2007, mostly at its laboratory in Pori, Finland, to give additional design confidence. This included flash flotation, gravity gold recovery, concentrate settling and filtration. Further supplementary testwork was undertaken by FLS Knelson in 2013 on gravity gold recovery and by Wardell Armstrong in 2015 on flotation concentrate. Solvay, in 2016, and Bureau Veritas Commodities Canada, in 2017, worked on selective flotation of copper from pyrite-rich ore. In 2014, Orway Mineral Consultants reviewed the testwork conducted by Aker Kvaerner to design the Skouries grinding circuit and conducted comminution circuit modelling studies using circuit simulations.
Historical operating data from the Skouries deposit is not available, as there has been no production from the deposit.
Source: Technical Report, Skouries Project, Greece, Eldorado Gold Corporation, effective date 22 January 2022. Section 1.9 Metallurgical testwork; Section 1.14 Recovery methods; Section 17 Recovery methods.
Consolidated report summaries
The following former standalone pages about this operation were consolidated here on October 25, 2026. They are retained for source traceability; dates and figures reflect each report’s own effective date and may be superseded by the current information above.
Skouries Cu/Au Project — 2011 Technical Report
This article summarizes the processing design and recovery approach for the Skouries copper/gold project as presented in the July 2011 NI 43-101 technical report, outlining the proposed conventional concentrator flowsheet and design cases.
Report context
The technical report, dated July 2011, details the Skouries Cu/Au Project process plant and infrastructure engineering, which was advanced from the 2007 Cost and Definition study. The design work was conducted by Outotec of Finland for basic engineering and ENOIA of Athens for basic and detailed engineering, under the direction of the project owner. The report covers plant design for open pit and underground ore feed schedules, defined design cases, and the process description.
Processing route
Plant scope and design basis
The process plant engineering scope includes surface ore reception facilities, primary crusher, coarse ore stockpile, grinding, gold gravity circuit, flotation, filtration, and paste thickening. Infrastructure includes administration, workshops, fuel station, welfare facilities, and power, water, and other services.
The project involves open pit mining for the first six years. Feed rate is 8 Mtpa for Years 1 to 5, with the remaining 7.0 Mt of open pit ore processed in Year 6. From Year 7, the plant will be supplied from underground operations at 6.4 Mt, then between 3.1 Mtpa and 4.8 Mtpa for at least the next 20 years. The plant design assumes a nominal throughput for harder underground material of approximately 881 tph. During Years 1–6, softer open pit ore is treated, and the selected mills accommodate the required tonnage.
The process plant design is based on a conventional flowsheet for porphyry copper ores, using proven equipment. Design margins and simple ore metallurgy are cited as providing a robust, low-risk processing solution. The Alumbrera mine in Argentina is referenced as a recent similar copper/gold operation.
Ore feed and products
Initially, for the first year, plant feed will be oxidised ore from the open pit. As near-surface oxidised ore is depleted, there is a transition to sulphide ore for the next five years from the pit. Thereafter, underground sulphide ore is extracted. Primary products are a high-quality gold-copper concentrate and gold doré ingots, estimated to contain approximately 30% of the gold in the ore feed.
Process description
The Skouries concentrator flowsheet comprises gyratory primary crushing, a coarse ore stockpile and reclaim system, single-stream SAG/Ball Mill grinding with cyclone classification, free gold recovery by gravity separation and doré production, flotation, tailings thickening and disposal, and copper/gold concentrate thickening and filtration. The design includes a pebble crushing circuit, coarse and fine free gold recovery circuits, and a doré production facility.
The coarse ore stockpile has a live capacity of 21,000 t, about 33% of total volume, and is covered and conical in form.
Evaluated design cases
Two design cases were evaluated by Outotec:
- Nominal design case: Processing underground sulphide ore.
- Second case: shows higher tailings and concentrate production scenario.
Both cases use the same feed grades and recovery assumptions, with the difference being the SAG pebble circulating load (0–25% for nominal, 50% for the second case).
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Cu in feed (%) | 0.54 | Life of mine average, both design cases |
| Au in feed (g/t) | 0.83 | Life of mine average, both design cases |
| % Cu in rougher concentrate | 5 | Design case |
| % Cu overall recovery | 91.1 | Design case |
| % Cu in final concentrate | 26 | Design case |
| % Au recovered by gravity | 30 | Design case |
| % Au overall recovery | 84.0 | Design case |
| SAG pebble circulating load (%) | 0–25 (nominal); 50 (high case) | Design case |
| Nominal throughput hard underground ore | ~881 tph | Design assumption |
| Open pit feed rate Years 1–5 | 8 Mtpa | Design schedule |
| Underground feed rate from Year 7 | 6.4 Mt, then 3.1–4.8 Mtpa | Design schedule |
| Coarse ore stockpile live capacity | 21,000 t (about 33% of total volume) | Design |
Project website: https://www.eldoradogold.com/investors/news-releases/eldorado-gold-announces-results-skouries-project-feasibility-study-after
Technical qualifications
The report provides several limitations and basis notes:
- The process plant design was advanced from the 2007 Cost and Definition study; the current design incorporates improvements reducing cut and fill requirements and capital cost.
- The plant design exceeds underground mining output, so operations will be based on campaign treatment to operate at optimum efficiency, allowing higher throughput if alternative or additional ore streams are identified.
- The design assumes nominal throughput for harder underground material at approximately 881 tph; softer open pit ore is treated during Years 1–6 with selected mills accommodating required tonnage.
- Design cases assume life of mine average feed grades of 0.54% Cu and 0.83 g/t Au, and both cases apply the same overall copper and gold recovery figures.
- The SAG pebble circulating load differs between design cases (0–25% versus 50%), affecting the tailings and concentrate production scenario.
Source: Skouries Cu/Au Project , NI 43-101 Technical Report, July 2011, Sections 17.1, 17.2, and 17.3 (Recovery Methods, Process Plant Engineering Overview, Process Description, Coarse Ore Stockpile).
