Zone 9 comprises five ore bodies with a total strike length of approximately 1,900 m and width varying from 2 m to 12 m. Vertically dipping mineralisation is structurally adjacent to the Lunnoye fault (located in its footwall) and is heavily brecciated in places. The most important ore mineral is quartz. Silver is present in the form of sulphides and sulphosalts, while gold is mostly found in free form. The quartz has a distinct white colour and is easy to identify visually. Silver and particularly gold grade distribution within the ore body are highly erratic, requiring significant in-fill and grade control drilling.

The Okhotsk-Chukot volcanic belt formed over 25 Ma (middle Albian-Cenomanian) (Belyi, 1994) at the boundary between the continental Verkhoyansk-Chukot and Koryak-Kamchatka terranes. This giant belt is 3000 km long is composed of subaerial volcanic rocks. Relative to the oceanic margin, the Okhotsk-Chukot belt is divided into the inner, outer, and perivolcanic zones. The intricate structure of terranes of the basement and the Okhotsk-Chukot belt produced a diversity of epithermal deposit types. The inner zone of the belt mainly accommodates porphyry Cu-Mo deposits. The outer and perivolcanic zones include gold-silver and silver-tin ore deposits. The gold-silver subtype is more widespread in the outer zone (Karamken, Valunisty, Kupol, and Dvoinoi). Deposits of the silver subtype (Dukat, Lunnyi, Arylakh, Golcovy and others) are confined to the volcanic rift located between the Yana Kolyma and Omolon terranes of the Okhotsk-Chukot belt.

The Lunnoye mine is accessible by two declines driven from the flanks of the ore body. A 10 m crown pillar separates the underground mine from the depleted pit. Underground conditions at the Lunnoye mine are challenging due to the proximity of the fault and, in some places, the significant brecciation of ore and hanging wall, which necessitate significant support structures. Most permanent underground workings are supported either by steel frames, where stability is poor, or by steel anchors and shotcrete, where conditions are moderate. Open stopes are supported by wire mesh and anchors. Ground conditions tend to improve at the lower levels of the mine as the ore body becomes more distant from the fault.

Both underground development and stoping at Lunnoye are fully mechanised, with the use of trackless equipment for drilling (long-hole production drill rigs and development jumbos), mucking (LHDs), and trucking (underground trucks). Ore is transported directly to the surface and then to the processing plant by contractors.

The Omsukchan concentrator uses conventional sulphide flotation technology, with each section designed to treat different types of feedstock. To achieve optimal results, extensive geotechnological testing is employed to determine the suitability of a particular ore for one of the sections and to assist in the selection of technological parameters (feed rate and reagent addition).

Section 1 is designed to treat simple metallurgical ores from the Dukat mine which typically yield higher recoveries with lower reagent consumption and generate concentrate that is amenable to cyanidation. The processing circuit comprises three-stage grinding (one SAG mill and two ball mills) followed by flash flotation and conventional flotation.

Section 2 is designed to treat ores that are technically more complicated, including feedstock from Goltsovoye, Lunnoye and old stockpiles. The processing circuit comprises two-stage grinding (one SAG mill and one ball mill) followed by gravity ........