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.
