The Skouries deposit is centred on a small (less than 200 m in diameter), pencil-porphyry stock that intruded schist and gneiss of the Vertiskos unit. The mineralized porphyry intrusion plunges steeply to the south-southwest and obliquely crosscuts the moderate to steeply north-east dipping limb of a district-scale F2 antiform. Mineralization has been tested to a depth of 920 m from surface as shown on Figure 7.3. Surface exposures and drill data indicate that the porphyry stock has a subtle north-east elongate geometry. The porphyry is characterized by at least four intrusive phases that are of probable quartz monzonite to syenite composition (Kroll et al. 2002; Frei, 1995) but contain an intense potassic alteration and related stockwork veining that overprints the original protolith. Potassic alteration and copper-gold mineralization also extend into the country rock; approximately two thirds of the Measured and Indicated Mineral Resources are hosted outside the porphyry with about a 50:50 split in gold-equivalent ounces. The potassic alteration is characterized by potassium feldspar overgrowths on plagioclase, secondary biotite replacement of igneous hornblende and biotite, and a fine-grained groundmass of K-feldspar-quartz with disseminated magnetite. Four main stages of veining are recognized:
• Early stage of intense quartz-magnetite stockwork (pre-ore stage).
• Quartz-magnetite veinlets with chalcopyrite ± bornite (initial ore stage).
• Quartz-biotite-chalcopyrite ± bornite-apatite-magnetite veinlets (main ore stage).
• Localized, late stage set of pyrite ± chalcopyrite-calcite-quartz veins (post-ore stage).

Skouries is typical of a gold-copper porphyry deposit. Mineralization occurs in stockwork veins, veinlets and disseminated styles typical of a porphyry, and has a subvertical, pipe-like shape. The multi-phase monzonite to syenite porphyries intruded into metamorphic basement rocks. Both igneous and metamorphic rocks contain high temperature potassic alteration (K-feldspar-biotite) and stockwork quartz-magnetite-chalcopyrite-bornite veins. The potassic zone in the surrounding country rock is surrounded by a high temperature inner propylitic alteration characterized by amphibole. The deposit, however, lacks extensive phyllic or argillic-advanced argillic zones typical of many porphyry systems. This may, in part, reflect a deeper level of erosion and the focused nature of the magmatic-hydrothermal system.

The Skouries Project is designed as a two-phase mining operation. Phase 1 consists of a combined open pit and underground mine, operating over nine years. Phase 2 consists of mining from the underground mine only, for an additional 11 years. The total ore producing LOM is 20 years.

Phase 1 total mill feed rate is 8.0 Mtpa, consisting of a nominal 5.5 Mtpa from the open pit mine combined with 2.5 Mtpa from the underground mine. At the start of the mine life, during the initial two-year underground mine ramp-up period, the open pit feed rate is variable in order to maintain the 8.0 Mtpa mill feed. During Phase 1, 8.0 Mt of low-grade oxide ore is stockpiled to be rehandled for mill feed during Phase 2. Phase 1 is completed at the end of the open pit mine life in Year 9.

Phase 2 mine production, from Year 10 to the end of the LOM, is provided from the underground mine. Phase 2 mine development begins in Year 4 in order to allow a seamless ramp-up from the nominal Phase 1 production rate of 2.5 Mtpa. During the first four years of Phase 2, the mill feed
rate of 8.0 Mtpa is maintained by reclaiming oxide ore stockpiled during Phase 1, at a rate which balances the mill feed to 8.0 Mtpa through Year 13. From Year 15, Phase 2 mill feed is maintained at a nominal feed rate of 6.5 Mtpa, solely from underground mine production, which tails off in
Years 19 and 20.

Open pit mining will be by conventional truck-shovel operation, with an ore production rate of approximately 5.5 Mtpa, at a waste to ore stripping ratio of 1.03 The mining sequence will consist of drilling, blasting, loading, and hauling of ore and waste materials for processing and waste
disposal. Based on the modelled rock types, approximately 17% of the mined material is amenable to free digging; this material will not be blasted.

Drilling operations will be carried out continuously as part of the normal mining operation. Once full mine production is reached, drilling and blasting of approximately 1 Mt (dry) per month will be required to maintain production levels. Drilling and blasting activities will be carried out by Hellas Gold, with bulk explosives and associated blasting accessories being delivered to site as needed by an explosives contractor.

Waste material classified as red clay and overburden will not be drilled or blasted as it is considered free dig material. All other waste and ore material types (weak rock and hard rock) will be drilled and blasted.

The primary haul roads are designed at 25 m width, based on a 90 t haul truck. Other haul roads, to be used by contractor trucks, are designed for 55 t articulated haul truck with an overall roadway width of 15 m. Table 16.5 outlines the road widths for each truck class. Road grades are limited to 10% in-pit and ex-pit for the 90 t trucks and approximately 12.5% for the contractor trucks. Runaway lanes will be constructed as required for safe operations. The smaller 55 t haul truck has been selected for waste as the route which the waste needs to travel over to the various dump areas is winding along steep terrain.

The primary mining loading fleet will consist of a conventional 12 m3 diesel hydraulic excavator and two front-end loaders with 8.5 m3 and 12 m3 buckets.

Underground mining
The Skouries orebody that extends below the bottom of the open pit is amenable to a bulk underground mining method and has been evaluated under several different design approaches since the late 1990s, including block caving, SLC, and SLOS. SLOS has been confirmed as the most appropriate underground mining method for a number of reasons.

The underground portion of the Skouries Project will begin from the existing ramp from the surface to 385 masl. The ramp is currently developed to 35 m above the first production level, 350L. Mining will proceed to the 350L to establish major infrastructure and services. The 350L will serve as the mucking horizon for two test stopes, which are situated in the Crown Pillar and within the mining limits to enable a mineralized and accurate representation of the mining to be completed in Phase 1.

Underground mining will be by conventional underground mining techniques. The mining sequence will consist of drilling, blasting, loading, and hauling of ore and waste materials. During Phase 1, ore will be hauled to the surface crusher by truck. During Phase 2 ore will be hoisted to surface by a shaft. In Year 4, the shaft headframe construction will commence, and shaft excavation will begin in Year 6. Excavation of the shaft will continue through Year 8, with the entire materials handling system projected for completion six months prior to the beginning of Phase 2 in Year 10.

The design of the Skouries mine includes provision for remote mining technology (RMT), which has an impact on the cycle times of stopes and the productivity of equipment. This technology includes tele-remote operation of mechanized equipment by an operator located on surface or in a remote area of the underground mine.

The Phase 2 materials handling will involve shaft hoisting of ore to surface. There are no vertical production nor development ore or waste passes included in the mine design; all broken rock will be loaded using load haul dumps (LHDs) and transported via the ramps in haul trucks. Shaft hoisting is critical to enable a ramp-up to full Phase 2 production of 6.5 Mtpa from the Phase 1 production of 2.5 Mtpa. In order to hoist the material by shaft, underground crushing will be implemented. During Phase 2, all stope ore and some late development ore will be hoisted to surface via the shaft. Development waste will continue to be hauled to surface via the dual ramp system, but these quantities are expected to be minimal.

- subscription is required.

For the first nine years of operation, the ore will be extracted from the open pit mine as well as from the underground mine for a total mill feed rate of 8.0 Mtpa. From the tenth year of operation until the 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 the copper / gold ore at a projected 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 that contains an average of 26% copper and 27 g/t gold. Metallurgical tests have shown that the ore contains a small amount of palladium (Pd), which will be collected into the copper / gold concentrate during flotation.

The process plant design provides for a nominal 8.0 Mtpa of ore throughput. While gravity classification, secondary gravity classification and gold room circuits have been designed, installation has been deferred pending confirmation of the need for gravity concentration to meet designed overall gold recoveries.

The unit operations comprise of:
• Primary crushing and crushed ore stockpile.
• SABC grinding and pebble crushing.
• Flotation and regrinding.
• Flotation concentrate and tailings thickening.
• Flotation concentrate filtering, storage and loadout.
• Tailings filtration, conveying and paste fill production.
• Reagent preparation and services.

Flotation is carried out in six stages:
• Rougher.
• 1st cleaner.
• Cleaner scavenger.
• 2nd cleaner.
• 3rd cleaner.
• Additional cleaning, in order to produce a clean copper / gold concentrate while achieving
satisfactory recoveries.

Concentrate regrinding is carried out by the regrind ball mill.

The regrind ball mill operates in closed circuit with a cluster of 14 hydrocyclones (250 mm diameter), 10 duty and four on standby. The operation of the regrind circuit will be controlled by the central distributed control system (DCS) of the plant.

The regrinding circuit is fed with the concentrates of rougher and cleaner scavenger flotation as well as the regrind gravity concentration tailings and additional cleaner concentrate. These are directed to the hydrocyclone cluster. The regrind cyclone cluster overflow will flow to the 1st cleaning circuit. The regrind cyclone underflow feeds the regrind ball mill.

The final concentrate of the 3rd cleaning flotation stage is directed to a concentrate thickener of 12 m diameter. Flocculant solution is added to increase the solids sedimentation rate. The solids concentration in the thickener underflow is typically 60% w/w. The underflow is pumped to filter presses for filtration.