The gold mineralization at the Aurora Gold Mine exhibits features analogous to mesothermal or “orogenic” gold deposits typified by Archaean deposits of the Abitibi region, Canada. Features characteristic of the gold mineralization at the Aurora Gold Mine include:
• A strong spatial association to large scale shear zones;
• Relative late timing during active compressional deformation;
• A strong spatial association to large scale shear zones;
• Formed during greenschist metamorphic conditions;
• Association with a propylitic-phyllic alteration assemblages; and
• Is principally hosted in quartz-ankerite pyrite veining.

Gold mineralization in the Golden Mile area is controlled by a series of northwest-southeast trending shear zones. These shear zones are orientated sub parallel to the dominant northwestsoutheast structural trend that occurs throughout the Aurora property. The shear zones contain a steep northwest-southeast trending foliation that formed during northeast southwest shortening.

The gold mineralization in the Golden Mile area is chiefly associated with quartz-ankerite veins containing minor pyrite and associated hydrothermal alteration. The auriferous veins form weak to moderate stockworks preferentially in competent lithologies outside the most intensely deformed and altered segments of the shear zones. The auriferous veins have undergone minor post formation deformation. The geometry of the auriferous stockworks is controlled by the geometry of the competent lithologies and the geometry of shear zones, or a combination of both.

The Aurora Gold mine area is divided into four major gold mineralization zones: Rory’s Knoll (includes Walcott Hill East), Aleck Hill (includes Aleck Hill North), Walcott Hill, and Mad Kiss (includes Mad Kiss West).

Open Pit Mining:

The open pit hasa mine life of 13 years based on a total of 19.0 Mt of ore mined at an average grade of 2.74 g/t. Approximately 55% of the ore tonnes are sourced from Rory's Knoll, 30% from Aleck Hill, with the remainder coming from the Walcott Hill, Mad Kiss and North Aleck Hill satellite deposits. Mining activity over the near term will be focused on fresh rock ore at Rory's Knoll.

The Company was able to successfully smooth the mining rate over the LOM with an average total (waste plus ore) rate of 70,000 tpd over the next four years and there after maintained at a steady 30,000 tpd rate over the remaining LOM. The average strip ratio over the life of mine is 8.9 to 1. The Company is reviewing strategic bids from contract miners to handle the waste stripping requirements, which is envisioned to bea 3-year campaign. Contract mining will allow the Company to save on the capital expenditure of a fleet not required beyond this stripping campaign,and based on initial proposals, is suggestive of reduced mine operating unit costs.

Underground Mining:

Rory's Knoll:
The Optimized LOM plan demonstrates improved economics through accelerating selective underground mining of higher grade stopes concurrent with open pit operations. Following a two-year pre-production period, underground mining at Rory's Knoll is expected to be fully ramped up in year 2022. Long hole open stoping ("LHOS") will initially target higher grade material between the bottom of the pit from-240 metres below river level ("mRL") and -460 mRL. In 2023, the Crown Pillar will be blasted and mining will then transition to sublevel cave mining (SLC) for the remainder of the mine life at an estimated average mining rate of 4,700 tpd. An improved mine schedule is expected to provide supplemental feed from the other satellite deposits later in the mine life which resulted in Rory's Knoll underground mining becoming deeper by approximately 200 metres than what the previous 2017 Feasibility Study envisioned.

Accelerating underground development is also expected to provide an ideal platform to potentially upgrade and expand the underground resource, especially at East Walcott where limited historical drilling has produced exceptional results. Initial underground mine development will be conducted primarily by contract underground mining experts. An extensive training and development program will allow the transition to an underground workforce that is expected to be composed of approximately 80% Guyanese Nationals over the life of the underground operations.

Satellite Deposits – Mad Kiss & Aleck Hill:
The Mad Kiss underground contributes an estimated 107,00 ounces (0.6 Mt at an average grade of 5.18 g/t Au) to the overall Optimized LOM Plan. Mad Kiss is expected to be developed concurrently with the Rory's Knoll underground with initial production expected in 2019 and continuing through to 2021. Mad Kiss will be mined via longitudinal LHOS froma depth of about -10 mRL to about -400 mRL.

The Aleck Hill underground is expected to contribute 153,000 ounces (1.1 Mt at an average grade of 4.28 g/t Au) to the overall Optimized LOM Plan beginning in 2028 and continuing through to 2033. Aleck Hillwill be mined through acombination of transverse and LHOS from a depth of about -140 mRL to about -500 mRL.

Material from mining operations will feed an apron feeder - primary jaw crusher system, which will produce a crushed product size of approximately P80 of 150 mm.

Feed material is hauled to the run-of-mine (ROM) stockpile (19,000 tonne capacity) adjacent to the primary crushing station.

The grinding circuit, upon completion of the second phase of the expansion, will consist of a SAG mill, a ball mill and gravity concentrators operating in closed circuit with a hydrocyclone cluster. The grinding circuit will operate at a nominal throughput of 362 t/h (rock ore feed), and produce a final particle size P80 of 75µm. The existing SAG mill is 7.9m in diameter by 5.6m effective grinding length driven by a 5.5MW motor. A new ball mill and two XD-20 gravity concentrators will be added to the grinding circuit. The ball mill will be 5.5 m diameter by 10.7 m effective grinding length driven by a 5.0MW motor.

The hydrocyclone cluster classifies the feed slurry into coarse and fine fractions. The coarse underflow flows to the new ball mill for additional grinding with an off-take to the gravity concentrators. With the expansion, four additional cyclones will be added to accommodate the higher slurry flow and the flow to the gravity recovery circuit. Two cyclones will be dedicated to the current QS30, and one cyclone will be dedicated for each of the two new XD20’s. The final mill product with a nominal P80 of 75 µm will flow by gravity to the thickener. The hydrocyclones have been designed with a 300% recirculating load to the ball mill.

The gravity recovery and intensive leach circuits will consist of three gravity concentrators (one 30” and two 20” concentrators) with a feed trash screen, gravity tailings pump box and tailings pump, feeding a concentrate hopper, and a skid mounted intensive leach reactor. The previous CS1000 intensive leach reactor will be replaced by a larger CS2000 intensive leach reactor.

The scalping screen prior to gravity concentration removes coarse particles and/or metal pieces that would otherwise fill the concentrator with lower grade material, reducing the capacity, and/or damaging the concentrator. Scalping screen oversize will be directed by a launder to the gravity tailings box. Periodically, the centrifugal concentrators will be bypassed and switched to flushing mode to recover the collected concentrate. Gravity concentrate will be leached to dissolve gold by contacting material with the leach solution in an intensive leach system. The leach solution will include sodium cyanide and caustic solution.

The leach solution will be mixed with the gravity concentrate in the reactor feed tank and the resulting pregnant solution will be pumped to the electrowinning circuit.

The ball mill hydrocyclone overflow will be fed by gravity to a vibrating trash screen for removal of trash material and then feed a new pre-leach thickener. A cross-cut sampler will be installed to collect a shift composite head grade sample for metallurgical accounting purposes. A flocculent make-up system will be installed adjacent to the thickener and flocculant solution (anionic polyacrylamide) will be added to the thickener feed to promote the settling of the solids. The thickener will have a diameter of 30 m and produce a thickened slurry product of 50% solids in the underflow. The underflow slurry from the thickener will be pumped to the leach circuit (No. 1 leach tank). The thickener overflow will report to the process water tank.

The thickener underflow will be pumped to a pre-leach screen to remove any trash ahead of the leach circuit. The intention is to relocate the existing pre-leach screen to the new first leach tank. The expanded leach circuit is designed to provide approximately 18hours residence time – three new leach tanks will be installed for a total of five leach tanks, each 13.2 m diameter by 13.2 m high, operating in series. The agitators have down-draft air addition from the leach blowers to provide air to the leach slurry. The new leach tanks will be installed with cone spargers for additional air injection. The slurry from the No.5 leach tank will overflow to the first of six existing 9.85 m diameter by 11.45 m high CIP tanks. The CIP circuit provides approximately 1.7hours per stage (total 10h) residence time at the planned 8,000tpd capacity. Each tank includes an agitator, carbon transfer pump and a new MPS650 interstage screen.

The existing MPS550 interstage screens can be converted to MPS650 units by a simple conversion, thus increasing the screen surface area from 5.5m2 to 6.5m2 to accommodate the higher flowrate.

The average carbon concentration in the CIP circuit is expected to be maintained at approximately 20 g/L. As the leach slurry proceeds through the circuit, metal values in the leach solution will progressively decrease as the gold is adsorbed on to the carbon. Loaded carbon will be transferred from the first CIP tank to the carbon elution circuit, based on a predetermined elution cycle and schedule. The carbon is transferred sequentially, between the CIP tanks, countercurrent to the slurry flow to maximize precious metal recovery.

Loaded carbon will be collected and transferred to the elution columns in discrete batches of up to 4 tonnes per column. The tailings stream from the CIP circuit flows by gravity onto a stationary safety screen to recover any carbon particles that may have escaped from the final CIP tank. Safety screen undersize product is then report to the CIP tailings cyanide destruction circuit.

Lime slurry will be added to the first and second leach tanks to maintain protective alkalinity at a design pH of 10.0 to prevent evolution of hydrogen cyanide gas (HCN). Air will be sparged from the bottom of the three new leach tanks and the new leach tank agitators will have down-draft air injection, similar to the existing tank agitators.

Two new blowers will be added to the existing blower facility to provide enough process air to the expanded leach circuit. The new blowers will be sized so that the leach tanks have sufficient air supply with one new blower operating in parallel with the existing blower (and one as standby).

The carbon stripping (elution) process utilizes a split-AARl method to produce a pregnant solution, which is pumped through electrowinning cells for gold recovery.

During the strip cycle, solution containing approximately 3% sodium hydroxide and 3% sodium cyanide at a temperature of 115°C (280°F) and 450 kPa (65 psi) is pumped into the column. Subsequently a hot solution of weak electrolyte solution, from the previous elution cycle is pumped through the column to de-adsorb the gold. This is then followed by a cold water wash to remove residual gold and silver in solution. This cold water wash solution becomes the weak electrolyte solution, collected in the weak electrolyte tank, for the next elution cycle.

Solution (pregnant solution) exiting the top of the elution vessel is cooled through the heat recovery heat exchanger. Heat from the outgoing solution is transferred to the incoming cold solution, prior to the cold solution passing through the solution heater. An electric boiler is used as the primary solution heater. The resulting pregnant solution flows to the electrowinning circuit to recover the gold and silver in solution.

Electrowinning will proceed on a batch basis with pregnant solution circulating through the EW cells for a specified time or until a pre determined solution gold value is attained.

The proposed plant expansion to 7,500 tpd will be completed in two phases. The first phase is expected to increase the hard rock throughput rate from 5,600 tpd to 6,600 tpd. The second phase of the expansion will allow the continued processing of 7,500 tpd of hard rock ore. It includes the utilization of a pre-crushing circuit and ball mill from a previously purchased 1,000 tpd modular processing plant.