The Wassa property lies within the southern portion of the Ashanti Greenstone Belt along the eastern margin within a volcano-sedimentary assemblage located close to the Tarkwaian basin contact. The eastern contact between the Tarkwaian basin and the volcanosedimentary rocks of the Sefwi group is faulted, but the fault is discrete as opposed to the western contact of the Ashanti belt where the Ashanti fault zone can be several hundredmeters wide.

The Wassa lithological sequence is characterized by lithologies belonging to the Sefwi Group and consisting of intercalated meta-mafic volcanic and meta-diorite dykes with altered metamafic volcanic and meta-sediments which are locally characterized as magnetite rich, banded iron formation (“BIF”) like horizons (Bourassa, 2003). The sequence is characterized by the presence of multiple ankerite-quartz veins which are sub parallel to the main penetrative foliation. The lithological sequence is also characterized by Eoeburnean felsic porphyry intrusions on the south-western flank of the Wassa mine fold.

The Wassa mineralization is subdivided into a number of domains, namely: F Shoot, B Shoot, 242, South East, Starter, 419, Mid East, and Dead Man’s Hill. Each of these represents discontinuous segments of the main mineralized system. The SAK deposits are located approximately 2 km to the southwest of the Wassa Main deposit on the northern end of a welldefined mineralized trend parallel to the Wassa Main trend. The mineralization is hosted in highly altered multi-phased greenstone-hosted quartz carbonate veins interlaced with sedimentary pelitic units.

Mineralization within the Wassa Mine is= structurally controlled and related to vein densities and sulphide contents.The mineralization generally consists of broadly tabular zones containing dismembered and folded ribbon-like bodies of narrow quartz vein material. Three vein generations have been distinguished on the basis of structural evidence, vein mineralogy, textures and associated gold grades.

The mine plan assumes underground mining will continue until the end of 2024 and that open pit mining will start in 2023 and continue until 2028.

Total ore material amounts to 18.6 Mt at an average grade of 2.46 g/t Au estimated to recover 1.5 million ounces of gold. This consists of: 7.5 Mt at 3.95 g/t underground; 9.9 Mt at 1.57 g/t open pit; and 1.2 Mt at 0.63 g/t from stockpiles.

The underground design utilizes a twin decline access from the base of the open pit which reduces the access to the mineralization from the surface topography. The selected mining method is sublevel open stoping utilizing unconsolidated waste backfill in the early stages and converting to cemented paste backfill in 2020.

A staged approach to ventilation is taken, with raises to surface completed in line with the development and production schedule.

Mining is undertaken using trackless, diesel powered equipment including twin boom jumbos for development and long hole drills for production drilling. The approach to materials handling to surface is through a combination of 17 t capacity loaders and 40 t capacity trucks.

The underground mine reached commercial production in January 2017 and, since that time, has shown consistent improvement in ore tonnage generation capacity. By the end of 2018, it was producing at a rate of 3,500 tpd, with plans to increase to close to 4,000 tpd in 2020.

Geotechnical conditions in the mine are very good with consistently low rates of unplanned dilution being achieved in the stopes and development.

As with most underground operations, there is a risk of flooding of the underground operation and significant effort has been expended to understand and mitigate this risk. Extensive hydrogeological studies have been conducted to inform the mine hydrogeological and geoenvironmental models. The pit catchment areas have been reduced through earthworks and drainage diversions around the pit areas to ensure minimal water ingress into the pits from the surrounding areas. The sump capacities in the pits below the holings into the underground have been designed to contain 100-year storm events over 24 hour periods. The pumping systems from the pits and underground are in the process of being upgraded to ensure enough capacity is available to dewater the sumps and the underground mine during and following such rain events.

A conventional approach to open pit mining is envisaged, employing excavators and trucks which are typical for this type and style of gold mineralization. Drilling and blasting of rock are conducted over bench heights of 5 or 6 m and explosives are delivered to the hole by the manufacturer. Oxide or weathered material is generally only required to be lightly blasted or, in some areas, can be excavated without blasting. Hydraulic excavators are used in conjunction with conventional blasting practice to mine a 2.5 or 3.0 m flitch height. Broken rock is loaded to 91 t capacity off-highway haul trucks to a central stockpile or to the waste dump.

The Wassa Mine was originally developed as a 3 Mtpa (8,200 tpd) open pit HL operation which operated from 1998 to 2001. In 2003, the plant was converted into a milling CIL circuit and started operation in 2005, treating a mixture of oxidized, fresh ores and material reclaimed from the HL pads.

From 2005 to the end of 2017, the plant processed at a rate 7,400 t/d primarily from oxide and fresh open pit feed. The earlier part of this period was characterized by high availability of oxide material and, from mid-2016, by the feeding of higher average grade underground material.

Currently, the treatment plant is processing ore from the underground operation in addition to low grade (“LG”) pit stockpiles at a rate of about 4,000 t/d. The plant consists of a crushing, milling, gravity and CIL gold recovery circuit.

The plant flowsheet has transitioned from the historical HL processing and currently consists of the following operations:

• A four-stage fine crushing circuit is employed incorporating an open circuit primary jaw crusher followed by secondary, tertiary and quaternary cone crushers with the secondary and tertiary crushers operated in closed circuit with sizing screens. A single secondary, two tertiary and four quaternary crushers give a nominal crushed product size from the crushing circuit of 80% <8 mm.

• Two independent milling circuits, each comprising a 5.03 m diameter x 6.7 m long ball mill fitted with 3 MW motors feeding individual clusters of classifying cyclones. Reported mill product size is around 70% <75 µm.

• Two separate gravity gold recovery circuits using 48” Knelson centrifugal concentrators process a portion of the classifying cyclone feed in each mill circuit.

• The gravity concentrate from the Knelson concentrators is retreated using a Gemini shaking table to produce a HG gold concentrate for direct
smelting, while the tails from the centrifugal concentrators and shaking table are returned to the milling circuits.

• Classifying cyclones and pre-leach thickener. The thickener underflow feeds a transfer vessel together with the secondary cyclone underflow where cyanide is added before the slurry is transferred to the CIL circuit. Oxygen is injected into the transfer line after the transfer pumps.

• A counter current CIL circuit. consisting of six stages of agitated vessel each of 2500 m3, gives an overall residence time of 18-20 hours at a 7,4000 tpd mill capacity. Hydrogen peroxide is added periodically to CIL tank 1 to maintain the dissolved oxygen level. Activated carbon is retained in each tank using interstage basket screens and is moved counter-current to the slurry flow using submerged vertical spindle pumps in each tank. Loaded carbon is recovered from the first CIL stage.

• Loaded carbon is acid washed and then stripped of gold using caustic soda in an 11.5 t pressure Zadra elution system with the gold electrowon onto steel mesh before smelting.

• Eluted carbon is thermally regenerated and returned to the last stage of the CIL circuit.

• The gravity gold concentrate and electrowon gold are smelted separately to produce gold doré bars.

• Additional supporting facilities include:

• Two, 2.1 tpd capacity pressure swing absorption oxygen plant located in the milling area of; and

• emergency diesel powered generators.