Ernesto/Pau-a-Pique mine complex (“EPP”) is comprised of multiple operating open pits (Lavrinha, Ernesto and Japones), an open pit mine under development (Nosde), and one underground mine (Pau-Pique).

Ernesto-Lavrinha is described as a detachment-style gold deposit that typically has the following characteristics:
-Gold mineralization is associated with low-angle to flat detachment faults, generally with a normal (extensional) sense of movement which consistently places younger units over older units;
-Mineralization is commonly characterised by quartz-rich vein and veinlet zones (in the ±25% range) with magnetite or hematite, coarse euhedral pyrite (in the ±1% range), sericite, some clay mineral, some late stage calcite and gold. The gold is commonly associated with only very small amounts of silver;
-Mineralization is typically located along a 3 m to 8 m thick rubble zone or mylonite of a detachment (or thrust) fault that intersects high angle structures, either faults or folds. The detachment is commonly within a deformed zone 10 m to 30 m thick;
-The continuity of the mineralization within the detachment zone is normally quite good, extending over 100 m;
-Detachment–style gold mineralization is in altered rock parallel to anticline axes and faults;
-Multiple styles of mineralization are common with local stacked mineralized zones;
-Fluid inclusion studies indicate temperatures of formation about 200°C to 250°C.

The Ernesto-Lavrinha Deposits consists of gold-rich quartz veins and veinlets occurring along a relatively thick, shallow-dipping structure at the base of the metasedimentary sequence and within altered sulfidic horizons in overlying meta-arenite units. The basal structure is interpreted to be a low-angle detachment fault that has been folded and faulted together with the overlying stratigraphy. Gold mineralization is located along asymmetrical anticlines and synclines that plunge gently to the north and are cut by NW and NE-trending narrow faults. The gold mineralization occurs in three zones: Lower Trap, Middle Trap and Upper Trap.

The Intermediate and Upper traps are in either permeable conglomeratic horizons or dilatent zones in the meta-arenite stratigraphy. Mineralization in the Upper and Intermediate traps is much less continuous than in the Lower Trap. The Intermediate Trap, which is about 80 m above the Lower Trap, is restricted to a conglomeratic horizon, where it intersects dilation structures developed by folding and faulting.

Mineralization in the Lower Trap is from 130 m to 210 m wide, with an average thickness of 5 m and is more-or-less continuous for at least 1,000 m along its northern plunge direction. The change in plunge angle appears to affect both the thickness and grade of the gold mineralization, with the thickest and highest-grade mineralization occurring where the plunge is less steep.

These zones have been defined by mapping and drill hole logging and sampling. The Lower Trap is within the detachment fault and includes the Ernesto resource referred to in this Report. The Lower Trap mineralized zone in Ernesto is widely developed within a mylonitic zone. The mylontic zone is a deformed version of meta-arenite which was altered and intruded by quartz veining. The mylonitic zone often resembles that of a healed fault zone that developed along detachment structures. The presence of extensional faulting in time of mineralization caused alteration footwall of tonalitic unit. The tonalite is extensively altered and represent of a weak rock which historically logged and called saprolite. However the mineralogical composition of this altered footwall unit is completely different from saprolite on surface. The footwall saprolites are mainly composed from clay minerals produced by alteration of feldspar and mica from tonalite groundmass. The dominant clay mineral is kaolinite.

The footwall saprolite is poor rock in terms of geotechnical characteristics. The alteration is gradational and kaolointic saprolite gradually changes to weakly altered tonalite. The altered tonalite has usually whitish color but groundmass of tonalite is recognizable in cores. However feldspar and micas are replaced by clay. The footwall saprolite is usually entirely replaced by clay minerals (kaolinite). Although in most cases fresh tonalite is located below footwall saprolite, in some local areas in Ernesto gradational changes from tonalite to saprolite both in upper contact with mylonite and lower contact with fresh tonalite are observed in core. This is another indicator of later movements along these detachment faults that accommodate weathering of protolith along weak contact with the mylonitic zone.

The footwall saprolite is weakly mineralized but there is no mineralization within fresh tonalite at Ernesto. This is an indicator that faulting and mineralization events are concordant.

Alteration associated with gold mineralization within the mylonitic unit includes abundant quartz veins and veinlets with coarse-grained euhedral pyrite and medium grained bipyramidal crystalline magnetite. In addition, there is saussuritization forming fine-grained sericite, chlorite, and carbonate. This alteration and mineralization occurs in mylonitic zones near the base of the detachment fault.

The Upper Trap, which is widely developed in the Lavrinha Deposit, occurs in metapelitic rocks (hematite sericite schist) in dilation zones of the intensely deformed synclinal troughs. The Upper and Intermediate traps share similar alteration and mineralization suites. The Upper Trap seems to be eroded in the Ernesto Deposit area.

Coarse gold is probably a factor in the Ernesto- Lavrinha Deposits, as indicated by the gravimetric recoveries used by the garimpeiros. Screen fire assays for gold in the seven samples collected from mineralized faces in the artisanal underground workings developed in the Lower Trap returned one sample with probable coarse gold.

The Ernesto mine would be developed to exploit the mineralized Lower Trap zone generally bounded by mine sections 8,303,792 NW and 8,304,172 NW and the 255 m and 365 m mine elevations.

The Ernesto Lower Trap zone is a gentle but variable dip and variable thickness deposit that strikes northwest and typically dips 15° to approaching 50° to the northeast.

The Lower Trap mineralization occurs within a mylonite-magnetite-sericite schist zone which is located between hanging wall metasediments and the footwall tonalite. The mylonite rock zone is 6 to 28 m thick and averages about 6 m thick. Saprolite (altered tonalite) is often present between the footwall tonalite and the lower contact of the Lower Trap zone. The saprolite is typically 10 m to 15 m thick in the centre of the proposed mining area and is thinner along the northwest, southwest and southeast margins of the proposed mining area. In addition, rafts of unaltered tonalite are at times present between the saprolite and Lower Trap zone.

Ernesto/Pau-a-Pique mine complex (“EPP”) is comprised of multiple operating open pits (Lavrinha, Ernesto and Japones), an open pit mine under development (Nosde), and one underground mine (Pau-Pique).

In December 2019, the company started mining operations at the high-grade Ernesto mine. In November 12, 2020, the Ernesto open pit mine, part of the Ernesto/Pau-a-Pique mine complex (“EPP”) declared commercial production effective October 1, 2020.

Ernesto Underground
Due to its nature of gentle and variable shallow dip and thickness, the Ernesto Deposit will be extracted by the Drift and Fill mining method, using a combination of drifting in ore and transverse primary and secondary small stopes in a 32%:36%:32% drift/primary/secondary tonnage ratio. The deposit is relatively close to surface at a maximum depth of approximately 170 m and will be accessed by one main ramp portal, with a second portal for definition drilling access and ventilation.

Backfill material will be waste rock for secondary stopes and ore drifts and cemented rock fill (“CRF”) for all primary stopes. Waste rock to fulfill the required backfill quantities will be obtained from two sources; the primary source will be from mine waste development and the second source will from the existing Ernesto open pit waste rock storage facility.

A six month pre-production period will be followed by approximately 3.5 years of production to mine an estimated 0.87 Mt of ore at an average grade of 5.03 g/t Au. Ore production will average 800 tpd.

The majority of underground mining activities at Ernesto will use Aura’s own employees, with external contractors or suppliers to undertake the supply of explosives, piping and services, ground support consumables, cement supply for the CRF plant, and other specialised tasks. Aura will have 100% ownership of all major fixed plant components used at Ernesto. Activities such as diamond drilling and other specialized activities or Project work will be contracted.

The EPP gold processing plant is located next to the Ernesto Deposit and is designed to treat up to 1 Mtpy feed. The flowsheet is based on a low-risk proven technological configuration for processing gold bearing ore.

A primary crusher located at the front-end of the process plant. Run-of-mine (“ROM”) feed will be blended and fed through the plant’s primary screen. The screen oversize is crushed and the combined crushed feed is ground in a single-stage, closed-circuit semi-autogenous grinding (“SAG”) mill.

Approximately 25% of the SAG mill cyclone underflow feeds a gravity-gold recovery circuit. The grinding circuit product is thickened and then pumped to a leach tank that is followed by six carbon-in-leach (“CIL”) tanks in series. CIL tailings are treated in a cyanide reduction tank where cyanide is chemically decomposed. Final tailings are pumped to a tailings storage facility.

Loaded carbon, recovered from the first CIL tank, reports to the desorption area. Gold is stripped from the carbon into a solution and electroplated from solution onto stainless steel cathodes. Dried cathode sludge and flux are mixed and smelted to produce gold bullion.

Haul trucks deliver run-of-mine feed to the ROM pad. A front-end loader is used to feed the crusher feed bin, which is fitted with static grizzly bars with an aperture of 600 mm.

Crushed feed, pebbles, cyclone underflow, and gravity concentrator tailings are directed to the SAG mill feed chute. The SAG mill dimension is 5.8 m in diameter, 5.8 m long and has an installed motor power of 2.65 MW.

The trash screen bypass box normally feeds the trash screen (0.8 x 18 mm aperture), but also allows slurry to bypass this screen. Trash screen oversize is directed to the trash bunker, while trash screen undersize slurry flows to the pre-leach thickener feed box. Dilute flocculant is added to the pre-leach thickener feed box and to the thickener feed well.

The CIL feed pump discharges thickened slurry to the CIL feed distributor. The feed to the CIL circuit is 50-52% solids by weight after the addition of lime, barren eluate and the flow from the gold room sump pump. The average flow rate of the CIL feed is 176 m3 /h (260 tph). Thickener overflow flows to the pre-leach thickener overflow tank and is then pumped to the process water pond.

The CIL area includes seven tanks in series: one leach tank followed by six CIL tanks for a total residence time of 24 hours.

The CIL feed distributor box normally discharges to the leach tank, but can also discharge to the first CIL tank. Launders allow the slurry flow to bypass any of the CIL tanks. The final CIL tank discharges to the cyanide reduction feed box.

The CIL feed distributor box normally discharges to the leach tank, but can also discharge to the first CIL tank. Launders allow the slurry flow to bypass any of the CIL tanks. The final CIL tank discharges to the cyanide reduction feed box.

The acid-wash cycle starts when the acid-wash column is full of loaded carbon. Concentrated hydrochloric acid is added to raw water to a concentration of 3% (w/w) in the column. The acid wash column is then allowed to soak.

The strip solution pump draws solution from the strip solution tank and primes the elution column. Sodium hydroxide and sodium cyanide are added to the strip solution at a concentration of 3% w/w each.

During preheating, the strip solution is pumped through the recovery heat exchanger (cold side), through the primary heat exchanger (cold side), and into the elution column. Solution leaving the elution column returns directly to the strip solution tank. The LPG-fired solution heater heats thermal oil, which is pumped in a closed circuit through the primary heat exchanger (hot side) indirectly heating the strip solution.

Elution starts when preheating is complete. During elution, solution leaving the elution column passes through the recovery heat exchanger (hot side) and to one of the eluate tanks. Elution continues until six elution column bed volumes (“BV”) have reported to the eluate tank. Raw water makes up the strip solution tank level during elution. Solution heating stops for the last BV, cooling the column and the carbon.

Excess water drains from the carbon in the 1.0 mm slotted-aperture regeneration feed dewatering screen. A screw feeder withdraws carbon from the feed hopper and feeds the carbon regeneration kiln. Regenerated carbon is quenched with water in the carbon quench tank and is then pumped to the barren carbon sizing screen by the carbon transfer pump.

Pregnant eluate and ICR pregnant solution report to the eluate tanks. The eluate pumps feed electrowinning cells during electrowinning and transfer barren eluate to the CIL feed distributor box at the end of an electrowinning cycle. Electrowinning cell discharge flows to the eluate return hopper and is then pumped back to the eluate tank(s).

A plant operator uses the gold room hoist to lift loaded cathodes up over the off-line cell. The operator then uses a high-pressure cleaner to loosen and wash the cathode slimes into the cell. The slimes flow into the pan filter and filtered sludge is put into an oven to dry. Dry sludge is mixed with flux and smelted in the barring furnace about once a week. Bullion bars are cleaned, sampled, weighed, and stored in a vault. The electrowinning cell exhaust fan vents air and mist from the cells to atmosphere outside the building during the electrowinning process. The furnace exhaust fan vents air from the furnace to the outside atmosphere during smelting. The gold room has four vent fans to ensure adequate ventilation.