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

Gold mineralization at Aurora is divided into four main mineralized zones; Rory’s Knoll, East Walcott and Walcott Hill, Mad Kiss and Mad Kiss West, and Aleck Hill and Aleck Hill North.

All the deposits display an association of gold mineralization with quartz veining and pyrite, locally as much as 10%. The auriferous veins developed relatively late in the deformational history and occur as brittle stockworks in more competent host rocks, e.g., Rory’s Knoll diorite and lesser quartz-feldspar porphyry dikes, and as foliation parallel, ribbon-like veins that vary in width from a few centimetres to rarely up to one to two metres wide.

At least three major generations of veining have been observed:
• Early quartz carbonate veins which are typically foliation parallel and folded or truncated.
• Brittle extensional arrays and stockworks – quartz-pyrite +/- ankerite, associated with mineralization.
• Late stage barren extensional quartz-calcite veins.

Coarse visible gold occurs in quartz-bearing veins and in pyrite-rich fractures. Gold-bearing structures have undergone minor post-formation strain. Vein selvages display sericite-iron carbonate hydrothermal alteration.

RORY’S KNOLL
Rory’s Knoll is the principal gold deposit at Aurora. The deposit is entirely hosted by a distinctive, highly altered diorite pipe.

The host diorite extends approximately 250 m along a trend of 325º, plunges approximately 70° northwest. The mineralization lies in a segment approximately 180 m by 120 m in plan view and is mineralized down-plunge to over greater than 2.0 km below surface.

Mineralization is associated with disseminated pyrite and quartz veins, which display a timing that is structurally late and likely syn-peak to post-peak metamorphism. Quartz is the primary constituent of veins, with lesser carbonate and sulphide minerals. The veins typically occur as extensional sets or as breccia style erratic veins and stockwork zones.

Minor accessory albite, chlorite, white mica, tourmaline, and scheelite can accompany the veins. Carbonates include calcite, dolomite, and ankerite. Gold mineralization at Rory’s Knoll is associated with pyrite, and lesser chalcopyrite, sphalerite, and molybdenite. Argentite, native silver, and bornite have been noted in polished section. Gold is usually associated with sulphide minerals but can occur as free gold.

EAST WALCOTT AND WALCOTT HILL
East Walcott is hosted by mafic volcanoclastic sediments and is located approximately 60 m southwest of the main Rory’s Knoll diorite pipe. The East Walcott zone consists of a series of tight fold closures over an area measuring approximately 100 m by 100 m in plan.

The geometry of East Walcott is controlled by the steep northwest plunging hinge line of fold
closures, which have a similar orientation to the Rory’s Knoll stock.

The style of mineralization is similar to Rory’s Knoll, hosted by stockwork zones and brecciated quartz-ankerite-pyrite veins in fold hinges. The highly foliated limbs also host narrow planar zones of layer parallel laminated veins.

The Walcott Hill deposit is located approximately 150 m west of East Walcott and extends southwest to over a distance of approximately 200 m. A number of historic adits, dating back to the 1940s, totalling approximately 327 m, were mined at Walcott Hill.

MAD KISS AND AREA
The Mad Kiss deposit is located approximately 500 m south-southwest of the Rory’s Knoll deposit. The mineralization occurs as extensional and foliation-parallel quartz-ankerite veining hosted by a foliated quartz-feldspar porphyry dike. The central portion of the dike is up to 300 m in length and varies in width from two to fifteen metres. The main body, on which the pit is centred, strikes 240° azimuth and dips approximately 70° northwest.

Mineralization is currently understood to be hosted within three separate mineralized shoots, which are segments of the porphyry that is offset across high strain zones. Mineralization has been intersected by drilling to a depth of approximately 700 m below surface.

The Mine is in operation with all production to date from open pit mining.

OPEN PIT MINING
Open pit mining has been underway at Aurora since 2015 using conventional open pit equipment. Work started with company crews using excavators and articulated 35 t to 45 t haul trucks. The mining fleet has been converted to 40 t fixed frame haul trucks. In 2018 the company crews were supplemented by contractors and the plan for the future may include all contracted open pit mining. The contractor operations will include pit and dump operations, pit dewatering, and road maintenance. Both, owner equipment and contractor fleet are operated by contractor’s personnel.

OPEN PIT DESIGN
Open pit mine design criteria are based on a conventional surface mine operation using 5 m3 backhoe excavators supported by 6 m3 wheel loader for ore and waste loading; and haulage by a mixed fleet of 35 t to 45 t capacity trucks.

The selected composite pit optimization shell was utilized to guide the pit design. The haul ramps are designed for the largest hauling equipment using the road. For two-way traffic the minimum overall ramp width, including shoulder berm and ditch, is 17 m. For the last four benches of the ramp in the pit bottom, the haul road is narrowed to a width of 12 m, suitable for single lane traffic. The maximum ramp gradient is 10%.

The design premise was to mine the pits to a minimum mining width of 30 m, then use a backhoe for the final narrow bench of the pit.

The Rory’s Knoll pit has been mined in five metre high benches in the past but is in the process of converting to 10 m benches in rock with ore mining in two 5 m high flitches if necessary, for ore control. The higher bench height will increase the potential pit production rate.

UNDERGROUND MINING
In 2019. there was a total of 914 m of underground development including 622 m of the Rory’s Knoll ramp access and related development and 292 m of waste and ore development at the Mad Kiss deposit.

The bulk of the underground mining potential at Aurora is beneath the Rory’s Knoll open pit. Lesser amounts of underground resources are present at Aleck Hill, Mad Kiss, and East Walcott Hill. Underground mining at Aurora is all planned to use rubber tired mechanized equipment.

RORY’S KNOLL UNDERGROUND
Rory’s Knoll is a steep dipping, nearly cylindrical deposit which demonstrates good continuity at the planned 1.7 g/t Au cut-off grade. Rock mass conditions in the ore are expected to be good with fair ground conditions in the sericite zones on the northeast and southwest sides of the deposit.

The planned method is a SLC variant. The Rory’s Knoll the hanging wall rocks are not expected to fail to the extent that they fill the void created by the removal of the ore. Rather, there will be dilution from the walls and from the open pit and a layer of ore will be drawn down over the life of the SLC operation.

EAST WALCOTT
The East Walcott area will be accessed via sublevels driven from the Rory’s Knoll access ramp. The plan is to mine the East Walcott by longhole stoping in 25 m sublevel intervals. The access drifts to the East Walcott may provide locations for infill drilling of the Rory’s Knoll ore body.

MAD KISS AND ALECK HILL
Satellite deposits (Aleck Hill and Mad Kiss) have the rock mass conditions and geometry to accommodate supported or unsupported longhole open stoping (LHOS), such as open stoping with pillars (partial extraction) or LHOS with backfill.

To reduce the mining costs and eliminate the need for cemented rock fill, the Mad Kiss and Aleck Hill deposits have been designed for longhole stoping with sill and rib pillars.

The crosscuts used in transverse stoping are driven perpendicular to the strike of the orebody, whereas in longitudinal development, the ore drives are driven parallel to the orebody strike. The ability for drifts to be driven perpendicular to the orebody in transverse stoping becomes beneficial when stope widths approach 20 m, as development costs can be minimized by decreasing the number of access drifts and crosscuts in waste.

CRUSHING FRESH ROCK
ROM ore from the mine is trucked to the ROM pad where it is dumped into the stockpile. The ROM ore stockpile is processed through two circuits: a single stage primary jaw crushing circuit and a pre- crushing circuit consisting of a jaw crusher and a secondary cone crusher.

The fresh rock crushing plant was designed for a nominal throughput of 500 t/h, representing 40% availability for the initial 1.75 million tonnes per annum (Mtpa) throughput. This circuit was sized to process the crushing requirements for the initial Stage 2 expansion to reach a throughput of 3.5 Mtpa.

ROM ore can be direct dumped or a Front End Loader (FEL) reclaims fresh rock ore from the ROM stockpile and dumps it into the 320 t capacity dump pocket that feeds the single stage jaw crusher. The dump pocket is protected by a static grizzly that has a nominal 800 mm sizing. Oversize material is rejected to the ROM pad. An apron feeder draws material from the dump pocket and discharges it into the jaw crusher.

The primary jaw crusher has nominal sizing of 1,600 mm x 1,200 mm with a 160 kW motor and was designed to operate with a closed side setting of 150 mm. Primary crushed product is conveyed to the 170 t (live) refeed bin by the jaw crusher discharge conveyor. The design of the refeed bin is such that:
• During periods of milling shutdown, the bin will overflow to the refeed overflow conveyor and is deposited in the 15,000 t to 20,000 t coarse ore stockpile.
• During crusher shutdown events, the material from the stockpile is fed with a FEL to the refeed bin. An apron feeder draws material to the SAG mill feed conveyor.
• During normal operation, ore is withdrawn from the refeed bin at a measured rate by the refeed bin apron feeder and discharged to the SAG mill feed conveyor.

SAPROLITE FEEDING SYSTEM
In the initial design, the saprolite ore was fed from the ROM stockpiles into the variable speed saprolite feeder breaker via a FEL. The separate feeding system was planned to prevent potential operational blockages of the jaw crushing circuit and provide a controlled blend of feed to the SAG mill. The feeder breaker was designed to break the saprolite ore down to a nominal top size of 200 mm. Broken ore then discharged to the Saprolite Conveyor which, in turn, discharges directly to the SAG mill feed conveyor and is blended with the fresh rock to feed the SAG mill at a predetermined blend of fresh rock to saprolite. A belt weightometer is provided to monitor and control the discharge rate from the saprolite feeding system by varying the feeder speed. The feeder breaker was removed from the circuit as it was not effective and subject to plugging.

PRE-CRUSHING CIRCUIT
The pre-crushing circuit uses the newly installed jaw crusher and secondary cone crusher to deliver finely crushed rock to the saprolite feeder system. The circuit consists of a Metso C110 jaw crusher and a Metso HP 300 cone crusher that operate in parallel to the original fresh rock crushing circuit. The capacity of the circuit is approximately 2,400 tpd. A FEL transfers ore from the ROM pad to the jaw crusher via an apron feeder. The crushed ore is conveyed to the cone crusher and discharge from the cone crusher it is conveyed to the existing, original saprolite feeder circuit and subsequently transferred to the SAG mill feed conveyor.

GRINDING
The Aurora milling circuit is a single stage SAG mill operating in closed circuit with hydrocyclones and a pebble crushing circuit. The initial design operated at a nominal ore throughput of 218.8 dry t/h with a mill availability of 93.0% and grinding to a nominal particle size of 68% passing 75 µm. With the newly installed pre-crushing circuit, the mill will process 7,500 tpd of mixed saprolite and fresh rock and maintain the same product size.

Ore discharging from the refeed bin apron feeder and the saprolite conveyor is combined on the SAG mill feed conveyor. The mill feed rate is measured by a weightometer on the conveyor and is controlled to a set point by varying the speed of the apron feeder.

The ore discharges from the SAG mill feed conveyor to the feed chute of the SAG mill and is mixed with process water and cyclone underflow slurry. Slurry from the SAG mill discharges through a trommel screen. Critical size pebbles discharge from the trommel oversize to a pebble crushing circuit. Undersize slurry flows by gravity to the cyclone feed pump box. Slurry is pumped to the cyclone cluster from the pump box. Larger cyclone feed pumps were added during the plant expansion to accommodate the higher flow rates. Cyclone overflow is directed to the leach circuit trash screen and into the leach/CIP circuit. Cyclone underflow is split. A portion of the flow is directed to the gravity circuit and the other portion is returned to the SAG mill feed.

The pebble crushing circuit consists of a pebble crusher feed conveyor that is fitted with a magnet to remove steel grinding balls from the conveyor. A self-cleaning magnet and a metal detector are provided to prevent steel from entering the pebble crusher. Discharge from the pebble crusher can either feed the pebble crusher or alternatively dump into a bypass chute that feeds directly onto the pebble crusher discharge conveyor. The pebble crusher discharge conveyor feeds onto the SAG mill feed conveyor.

The SAG mill is a grate discharge high aspect ratio design, having 5,500 kW installed power with a variable speed drive. Grinding media is loaded into a front end loader for tipping into the refeed bin.

The processing plant at Aurora was commissioned in 2015 and reached commercial production in January 2016. It was designed by Sedgman Limited (2013) with modifications to the design made by JDS and the Mine in 2017 and 2018. The pre-expansion plant included:
• Single stage primary crushing circuit utilizing a jaw crusher
• 15,000 tonne to 20,000 tonne crushed ore stockpile and re-feed bin for storage and surge management
• Separate saprolite crushing circuit including a feeder breaker (feeder breaker subsequently removed from circuit)
• 5,500 kW SAG mill including a pebble crushing circuit
• Gravity concentration circuit including centrifugal concentrator and intensive cyanide leaching of the concentrate
• CIP circuit including two leach tanks and six carbon adsorption tanks
• Four tonne carbon elution circuit
• Cyanide detoxification circuit with two tanks and final tailings pumps
• All required reagents and plant services including power s ........