The Mangazeisky Property contains two main deposit types: epigenetic polymetallic silver-lead-zinc veins (metasediment hosted), and porphyry (copper, gold, silver). The majority of the exploration, and the existing resources, are focused upon the polymetallic silver-leadzinc veins. The veins are sulphide-rich, containing sphalerite, galena, silver, and sulphosalt minerals in a carbonate and quartz gangue.

The Property contains several explored areas that host more than 100 occurrences of mineralisation. The mineral occurrences are concentrated within a 35-km long corridor. These main mineralised areas include: Yasny, Burny, Mukhalkansky, Zabyty, Zabyty-2, Mangazeisky, Strezhevoy, Vertikalny, Porfirovy-Borisovsky, Vostochny, Nizhny Endybal (NizhneEndybal), VerkhneEndybal, Jilny, Bezymyanny, Orogondia and Kis-Kue.

The mineralization of Mangazeisky North is mainly associated with banded brecciated textures. The following minerals are present: Native silver, acanthite, stephanite, polybasite, canfieldite, pyrargyrite, miargyrite, diaphorite, tetrahedrite, owyheeite, freieslebenite, boulangerite, arsenopyrite, sphalerite, pyrite, galena and chalcopyrite. The veins are strata-bound, occurring on contacts between strata, particularly around sandstone units, and tend to be dilated towards the hinge of the local fold structure. It is noted that the strongest silver mineralisation occurs within the central core of the veins, this also correlates with the zones of strongest oxidation.

The Vertikalny vein has been traced on surface for 5.1 km. The under-explored southeast portion, identified in 1990 by Yangeologia, possibly extends to the Endybal River valley. To the northeast, along the areas where oxide material is identified, the vein swells from 3 to 15 m. Further northeast, the zone splits into two. The eastern branch, which is obscured by a siltstone bed, was traced by individual grab samples in erosional windows. The mineralisation occurs as sandstone breccias with quartz or siderite cement, abundant hydrous ferric oxides that results from the oxidation of sphalerite and galena.

The Zabyty occurrence was discovered in 1934 and further explored in 1992 to 1994. Mineral occurrences are concentrated on the walls and in the watershed of the Fedor-Yuryage River. Mineralisation occurs as a structurally disturbed zone that intersects stratigraphy under a gravelite layer in the same stratigraphic level as the Strezhevoy mineralised body. The total width of the steeply dipping zone is 50 to 60 m (up to 2 km), striking at 315 to 340º. A single trench, developed by JSC Yangeologia in 1991, returned 1,906.5 g/t silver, 59.3% lead and 1.85% zinc from sandstone breccia cemented with sulphides.

The sediments above the stocks contain veinlets of sphalerite. The stock itself hosts quartz-galena-chalcopyrite veinlets, brecciated intermediate dykes, brecciated sandstone with argentiferous healed with galena-quartz cements, oxidised intrusive with disseminated sulphides. In most cases the stock is obscured by the overlying sediments.

Based on data by V.V. Shoshin (Nekrasov. et al. 1997) mineralisation at Orogondia is connected with a near conformable mineralised zone of shearing with a strike of 325 to 345° that can be traced for up to 4 km. Most of the mineralisation reports on the surface of medium-grained sandstones as sulphide-quartz-siderite veinlets, of 0.5 to 2 m wide (average thickness is 0.8 m).

This zone is a complex vein system of approximately 600 m in length with a thickness of up to 5 m, but averaging approximately 0.9 m. The thickness of the individual veins within the larger vein system varies from 10 to 20 cm. In addition, parallel mineral zones are associated with the main deposit. The average grade of silver of the zone is 2,652 g/t. The mineralised veins are situated within medium and coarsegrained sandstones and siltstones, overlying a lower conglomerate unit. A significant amount of a black organic substance (shungite) is present in the cement, binding the particles of the sedimentary units together. In the areas where there has been hydrothermal reworking of the sandstones, shungite forms lenses and flakes in association with coarse-crystalline drusy quartz. The underlying layers of sandstone contain disseminated silver mineralisation and are within the same stratigraphy as the Nizhny Endybal deposit.

The Mukhalkansky mineralisation is represented by two galena bearing veins. The first vein, which cross-cuts the stratigraphy has been traced for 800 m and has an average width of 0.2 m and contains an average silver content of 1,295.4 g/t. The vein is confined to a tectonic fault that was accompanied by brecciation of the enclosing rocks during its formation. The vein is orientated parallel to the Nuektaminsky fault and is believed to be its mineralisation supplying fragment. The second vein is a concordant vein in its mode of occurrence and is confined to a stratum of thin layer sandstones. The second vein branch can be traced for approximately 500 m and has a width of between 0.2 and 0.4 m. The average silver content of the second vein is 2,328.7 g/t.

The Bezymyanny mineralisation is composed of several zones confined to inter-stratal ruptures. The mineral veins are located along the contacts of medium-grained and fine-grained sandstone strata. Veins are traced for 500 m with a thickness ranging from between 2 to 5 cm and 34 to 40 cm. The mineralisation content varies from 756 to 24,433 g/t silver, 0.4 to 1.5 g/t gold, 0.1 to 7.81% lead and 0.1 to 0.8% zinc.

The Nizhny Endybal deposit has been known since 1774 under the name “Kokovin Silver Mine”. The style of the mineralisation at Nizhny Endybal takes the form of a stockwork style network of thin veins, as illustrated in Figure 7.7. Concentrations of the stockwork are accumulated into lens shaped bodies as shown in Figure 7.8. The mineralisation is associated with siderite veins, which are principally parallel or subparallel to bedding. However, occasional sub-vertical veins are present, which crosscut the bedding planes. The veins are predominantly 1 to 2 cm in thickness, but occasionally up to 10 to 15 cm. The thicker veins include veinlets of fahlore and vugs filled with fahlore crystals. Galena may also be present as separate veins, but the silver mineralisation does not appear to be directly related to the presence of galena.

The watershed of the Sirelendge-Fedor and Yuryage rivers is prospective for silver mineralisation. Several grab samples selected from among frost heave, characterise disseminated and vein-like mineralisation in altered sandstones.

Mineralisation in the Porfirovy area is associated with quartz, quartz-carbonate and quartz-sulphide veins and veinlets hosted by rhyolite and dacite porphyry. The copper and gold potential of the area has only recently been recognised and the copper-silver soil geochemical results indicate an anomalous area that corresponds with the intrusive complex. Locally the rhyolite has been silicified and the feldspars exhibit argillic alteration.

The Vertikalny deposit is currently being extracted by open pit mining techniques, whereas the Mangazeisky north deposit is greenfield and has yet to be mined.

The deposit will be mined in a north zone (Mangazeisky) by open pit, and a central zone approximately 6km south-southwest named Vertikalny which will be mined by open pit and underground methods. Vertikalny will comprise a sequence of four individual pits developed along strike of the mineralised vein with underground mining commencing beneath the main part of the central zone with the final underground drive (Zone 4) extending northwards.

A combined open pit and underground production schedule:
- Mining in the Vertikalny open pit anticipated for completion in Q4 2021;
- Mining at Mangazeisky North anticipated to commence in Q3 2021 with production ceasing in Q3 2023: and,
- Underground pre-production development anticipated to start in Q2 2022 with stope production commencing in Q4 2023.

The Mangazeisky pit has an overall strike length of 650m, maximum width of 250m, and a pit floor elevation of 1084m. Vertikalny will be developed as four pits along strike, the pits range from Pit 2 (smallest) with dimensions of 50m width and 120m length to the largest (Pit 4) in the northwest which is 145m width and 530m length. The respective floor elevations of these pits are 1117m Above Datum (AD) and 1094mAD.

Open Pit
Two individual pits have been designed along the strike of the Vertikalny deposit; in-line with the selected optimal pit shell. The portion of the pit shell extracting material from the south eastern extent of the mineralised zone intercepts a hillside. A conceptual cut & fill (CAF) road has been designed along the hillside to provide an initial indication of the access requirements to this area.

The Mangazeisky North deposit is situated some 6.5km NNW of the Vertikalny Pit. The pit shell is located on the brow of a hill approximately 130m above the valley floor. A conceptual cut & fill road was designed along the hillside to provide an indication of pit access requirements.

Underground Mining Method
WAI propose to maintain the mining methodology outlined by Tetra Tech; mechanised sub-level open stoping (SLOS). The method offers favourable results in safety, cost and dilution control as outlined by Tetra Tech. Stopes will be extracted in a retreat, top-down sequence, with adequate in-situ rock pillars left unmined for localised and regional stability.

Stope shapes were defined using the Datamine Mineable Shape Optimiser (MSO) module. MSO generates a set of practical stope shapes around a geological block model in accordance with a supplied cut-off grade and a set of geometrical constraints.

ROM mineral with a maximum size of approximately 300 mm and 80% passing 200 mm will be trucked to the ROM pad, and the material will feed into the crushing and screening circuit. The crushing and screening unit will be arranged for closed circuit crushing. The crushing circuit will operate over a single 12-hour shift to allow for maximum efficient running of the circuit crushers, which have been sized as per the standard crusher supply.

The ROM mineral will feed to a vibrating grizzly where the fine ore will be removed and passed directly to the secondary crushing circuit screen. The coarse fraction will be crushed in the primary jaw crusher, such as a Metso C80 or equivalent. The product from the jaw crusher will be sent to the secondary crushing circuit screen.

The secondary crushing circuit will contain a secondary cone crusher, such as Metso GP100 or equivalent, operating in closed circuit with a single deck screen to produce a final screen product with a P80 of 13 mm, suitable for the ball mill feed. The screen undersize from the secondary crushing circuit will be conveyed to a crushed ore bin where it will be reclaimed and fed to the processing plant as required.

The crushing circuit is designed to operate at 75% availability to allow for operational and mechanical maintenance and winter shut down. Spare sets of jaw and cone crusher liners will be kept on site.

The crushed material will feed directly onto the ball mill via a feed conveyor belt and feed hopper. The conveyor belt will be equipped with a weightometer and a sampler from which the primary accounting information will be obtained (i.e. the throughput, silver head grade, and moisture content).

The estimated size of the ball mill is 2.8 by 4.9 m installed with a 475 kW motor. Steel ball grinding media will be added to the ball mill feed using a wheeled crane and kibble, with the balls added to the mill feed hopper. Water will be added to the mill feed inlet to achieve an operating mill pulp density of approximately 60 to 65% solids by weight.

The process design is based upon the original Tetra Tech design in the feasibility study but with some modifications introduced by SBR. EMC Mining developed the final process design and detailed design documentation for construction. The original Tetra Tech design was based on the processing of oxide ore only, but with recommendations to modify the plant for processing sulphide ore.

Oxide Ore
A gravity circuit was incorporated in the original design using a Knelson concentrator with regrinding and intensive cyanide leaching of the concentrate. However, the gravity circuit was not subsequently installed by SBR.

The grinding circuit incorporated two-stage hydrocyclones (classification and dewatering cyclones) but the dewatering cyclone was replaced with a dedicated pre-leach thickener, to achieve a nominal 50% solids pulp density required for leaching. The original leach circuit required six tanks for a design residence time of 72 hours. However, with the excl ........