The Kupol and Dvoinoye orebodies are both high grade gold-silver vein deposits, and both are currently underground mining operations.

The Kupol deposit is located in the 3,000 km long Cretaceous Okhotsk-Chukotka volcanogenic belt. This belt is interpreted to be an Andean volcanic arc type tectonic setting, with the Mesozoic Anui sedimentary fold belt in a back-arc setting to the northwest of the Kupol region. Russian 1:200,000 scale mapping indicates that the Kupol deposit area is centred within a 10 km wide caldera, along the northwestern margins of the 100 km wide Mechkerevskaya volcano-tectonic “depression”, an Upper Cretaceous bimodal nested volcanic complex. The volcanic succession in the area is 1,300 m thick and consists of a lower sequence of felsic tuffs and ignimbrites, a middle sequence of andesite to andesite-basalt flows and fragmentals capped by felsic tuffs and flows.

The property is underlain by shallow eastward dipping andesite lithic tuffs, feldspar hornblende porphyry andesite, and andesite-basalt (trachytic andesite) flows. The andesitic volcanic units are intruded by massive to weakly banded rhyolite dykes, rhyolite and dacite flow-dome complexes, and basalt dykes. The main deposit strikes north-south and has been divided into six contiguous zones. From north to south these are: North Extension, North, Central, Big Bend, South, and South Extension.

The Kupol deposit is considered to be an example of a low-sulphidation epithermal deposit. Low-sulphidation epithermal deposits are high-level hydrothermal systems, which vary in crustal depths from depths of about 1 km to surficial hot spring settings. Host rocks are extremely variable, ranging from volcanic rocks to sediments. Calc alkaline andesitic compositions predominate as volcanic rock hosts, but deposits can also occur in areas with bimodal volcanism and extensive subaerial ashflow deposits. A third, less common association is with alkalic intrusive rocks and shoshonitic volcanics. Clastic and epiclastic sediments in intra-volcanic basins and structural depressions are the primary non-volcanic host rocks.

Mineralization in the near surface environment takes place in hot spring systems, or the slightly deeper underlying hydrothermal conduits. At greater crustal depth, mineralization can occur above, or peripheral to, porphyry (and possibly skarn) mineralization. Normal faults, margins of grabens, coarse clastic caldera moat-fill units, radial and ring dyke fracture sets, and hydrothermal and tectonic breccias can act as mineralized-fluid channelling structures. Throughgoing, branching, bifurcating, anastomosing and intersecting fracture systems are commonly mineralized. Mineralization forms where dilatational openings and cymoid loops develop, typically where the strike or dip of veins change. Hanging wall fractures in mineralized structures are particularly favourable for high-grade mineralization.

The mineralization typically includes pyrite, electrum, gold, silver, and argentite. Other minerals can include chalcopyrite, sphalerite, galena, tetrahedrite, and silver sulphosalt and/or selenide minerals. In alkalic host rocks, tellurides, roscoelite and fluorite may be abundant, with lesser molybdenite as an accessory mineral.

The Dvoinoye gold-silver deposit is located within the Okhotsk–Chukotka Volcanic Belt (OCVB), an Andean-type continental margin magmatic arc that extends southwest from the Chukotka Peninsula along the East Asian coastline. The OCVB has four distinct segments: two roughly northwest trending segments separated by a longer northeast trending zone and a shorter northeast zone at the far southwest end.

Host rocks at Dvoinoye are Late Cretaceous intermediate-felsic volcanics of the Tytylveyem Suite, which is divided into three units. At Zone 37, the host rock is assigned to the lower unit of the Tytylveyem Suite. The main host rock here is porphyritic dacite lava, containing 20% to 30% phenocrysts (plagioclase, pyroxene and potassium feldspar), in a siliceous aphanitic matrix. Other components of the local geology include crosscutting pyritic hydrothermal breccias that may mainly affect the tuff units. Their distribution and geometry are unclear but at least part of the Zone 37 vein is hosted by narrow siliceous pyritic milled breccias that may be related to larger volume hydrothermal breccias.

The Dvoinoye veins are close to the northern margin of the Ilirney granitic massif. As a result, there is substantial development of dykes, sills, and plugs of generally granitic composition.

Dvoinoye is a low sulphidation epithermal gold-silver vein deposit. The principal vein at Dvoinoye strikes at 040° over a length of at least 800 m. Ore zone width ranges from a few metres to more than 30 m in the central shoot. The vein has been drilled over a vertical extent of about 350 m (including sills). The vein system has a steep to subvertical dip to the southeast. There is evidence that at depth the vein system may shallow in dip, from subvertical to about 70°. There are two main thick quartz veins, within a variably wide envelope of narrower veins and veinlets (stockwork zone). The central shoot represents a blowout in width where the shoot may have a pipe-like form. The bulk of the gold is in the central shoot. At depth and at the southwestern end, the mineralization forms a series of sub-parallel veins, rather than one or two wide veins. Late to post vein block faults probably disrupt vein continuity along strike, especially to the northeast where the fault-bounded granite intrusion is developed.

Mineralization is characterized by low total sulphide content, generally less than one percent, by variable but low gold:silver ratios (average 1:1), and by the presence of considerable free gold in parts of the deposit. The main ore minerals and related sulphides in the vein are native gold, freibergite, pyrite, chalcopyrite, galena, and sphalerite, with minor acanthite. Ore minerals are generally fine-grained. Gold occurs inter-grown with sulphides, free in quartz-illite aggregates, and in places as rare dendritic growth bands.

A wide variety of vein and mineralization textures are recognized, including massive vein, colloform-crustiform banded vein, breccia, and veinlet/stockwork zones. The vein mineralogy consists of quartz-chalcedony (80% to 90%), adularia (5% to 7%), carbonate (up to 5%), illite, and chlorite. The main vein displays a lateral and vertical zonation in mineralization and alteration assemblages, reflecting the evolution of the system spatially and over time. Four styles of gold mineralization have been identified: pink quartz gold; carbonate-base metal gold; chalcedony-ginguro gold silver; and green quartz breccia.

Long hole longitudinal retreat sub level open stoping (the Avoca method) is used at both Kupol and Dvoinoye. In addition a limited amount of transverse sub level open stoping is also used at Dvoinoye.

Kupol Equipment
The following list outlines the major equipment fleets that are currently being used for
underground mining at the operation:
3 Toro T1400 loaders
5 Cat R1300 loaders
7 Cat R1700G loaders
13 Cat AD45B haul trucks
6 Sandvik Axera D7-240C development drills
4 Sandvik Solo longhole drills
7 Sandvik Robolt rock bolters
2 Sandvik Cable bolters DS420-C
1 Marcotte M40 shotcrete truck
1 Marcotte M40 super skin truck
1 Normet Charmec 1610B super skin
4 Normet utility trucks.

Dvoinoye Equipment
3 Sandvik - DD 420-40C jumbo rigs
2 Sandvik - DL 420-10C solo rigs
3 Sandvik - DL 420-10C robolt rigs
2 Atlas Copco -DIAMEC U6 diamond drill rigs
1 Atlas Copco - ECM660 surface drill rig
1 Caterpillar R1300G underground load-haul-dump (LHD)
5 Sandvik LH514 underground LHDs
1 Sandvik LH307 underground LHD
2 Tamrock EJC430 underground haul trucks
4 Sandvik TH430 underground haul trucks
3 Kamaz 20 t haul trucks
15 Iveko 40 t haul trucks
2 Kumatsu WA 500 surface loaders
2 D375 dozers
1 PC400LC excavator

The Kupol processing plant also processes ore from Dvoinoye. The ores from the two sites are processed in batches, with Dvoinoye ore typically being processed at the start of each month.

The milling process consists of primary crushing and a semi-autogenous grinding (SAG) mill / ball mill grinding circuit, and includes conventional gravity technology followed by whole ore leaching. Merrill-Crowe precipitation is used to produce gold and silver doré bars. Countercurrent decantation (CCD) wash thickeners recover soluble gold and silver, and a cyanide destruction system is used to reduce cyanide concentrations to an acceptable level for disposal. The tailings flow by gravity through a pipeline to a conventional tailings impoundment. Doré bars are shipped to the non ferrous metals plant in Krasnoyarsk. Average mill recovery, based on both Kupol and Dvoinoye ore, is 95% for gold and 85% for silver. The mill availability is 94%.

The mill is designed to process ore on a two shift per day, 365 days per year schedule, at a rate of approximately 4,500 tonnes per day or 1,642,500 tonnes per year.

Ore is trucked from the mine to a stockpile and transferred to a coarse ore bin using a front end loader. From the stockpile, ore is fed via grizzly screens (bars spaced 700 mm) into a coarse ore bin of 150 tonnes. Coarse ore is then conveyed to a Birdsboro-Buchannan jaw crusher with a discharge opening of 150 mm. Crushed ore is conveyed to a crushed ore bin with 3,500 m³ capacity.

Two apron feeders are provided below the crushed ore bin to feed ore to the SAG mill feed conveyor. The first stage of grinding is wet semi-autogenous grinding in a Koppers (Metso) mill (7.0 m diameter x 3.0 m effective grinding length) in a closed circuit with a vibrating screen for 2 mm primary grind size.

Screen oversize is sent back to the SAG mill feed conveyor and screen undersize is fed to nine Krebs hydrocyclones for further size control. Hydrocyclone underflow reports to the ball mill Koppers (Metso) (5.0 m diameter x 9.2 m effective grinding length).

Hydrocyclone overflow product is at a grind size of 80% minus -0.075 mm.

A gravity gold recovery circuit is located within the grinding circuit. Slurry is pumped from hydrocyclone feed sump to two centrifugal gravity concentrators (Knelson KCXD30) equipped with a control unit to vary operation mode and flush cycle. Concentrate is further processed at a gravity table. As concentrate builds up it is refined to concentrate bars.

Hydrocyclone overflow with solid content of 15% flows by gravity to the surge tank. From the surge tank, slurry is pumped to an EIMCO deep-cone thickener equipped with an agitator drive. Flocculent is added to get a clear overflow and to enable solids sedimentation. The thickener circuit overflow is pumped to a grinding circuit to be used as process water. Underflow with solids content of 50% is pumped to a pre aeration tank. The pre-aeration tank is equipped with a covered and ventilated agitator to stir slurry. The slurry then flows by gravity into the first of six leaching tanks for gold and silver to be dissolved.

The six leaching tanks are equipped with agitators to stir slurry. All leaching tanks are covered and provided with exhaust ventilation. The design of the leaching circuit ensures that slurry flows by gravity from one tank to another due to the descending top levels of tanks. Overflow from the last leaching tank is pumped to the first CCD thickener tank. Cyanide solution is added to the first, second and third leaching tanks at an adjustable flow rate. Lime milk is added to the pre-aeration tank, and the first and third leaching tanks. Lime is required to adjust pH level, while cyanide is added based on silver and gold content. Lead nitrate is added to the pre-aeration tank, and the first and second leaching tanks.

Pregnant solution residue tails are removed in a CCD circuit in five stages. The circuit comprises five EIMCO deep-cone thickeners equipped with agitator drives. The underflow of thickener tanks at each stage is pumped to a tank and mixed with the previous stage thickener with a solid content of 50%.

Barren solution from the Merrill-Crowe circuit is pumped to a slurry/solution mix tank under the last CCD thickener tank, as a washing solution. The first thickener overflow, the pregnant solution, flows by gravity to the pregnant solution tank.

Pregnant solution is pumped to pressure leaf clarifiers to remove suspended solids. Clarified pregnant solution is transferred immediately to the de-aeration tower MerrillCrowe process. The de-aerated solution is mixed with zinc dust (for gold and silver to be precipitated) and pumped to a filter press in the refinery area. After being pressed in the filter, the barren solution is pumped to a tank to be used for washing.

When filters are caked with solids, they are taken out of operation to be cleaned. The cakes are dried, and fluxes are added before further refinement in an induction furnace to produce doré bars.

CCD thickener number 5 underflow is pumped to a hypochlorite cyanide destruction tank; from this tank the slurry flows by gravity to the tailings impoundment.