Sulfide gold mineralization at Fosterville is relatively homogenous with orogenic gold deposits, however with minor variations in the host rock type and structural setting. Deposits similar to Foserville form a subgroup of orogenic gold deposits that are typified by gold occurring in fine crystals of arsenopyrite and/or pyrite disseminated in country rocks as a selvage to faults or veins. These deposits and classic vein-hosted deposits are effectively end members with many orogenic gold deposits displaying features of both.

Sulfide gold mineralization at Fosterville is controlled by brittle faulting. These brittle faults are stacked, generally steeply west-dipping with reverse movement varying from a few meters to over 150m. In the upper parts the fault system a series of moderately west-dipping reverse splay faults occur in the footwall of the Fosterville Fault. Sulfide gold mineralization occurs as disseminated arsenopyrite and pyrite forming as a selvage to veins in quartz – carbonate veinlet stockwork. The mineralization is structurally controlled with high-grade zones localized by the geometric relationship and interactions between bedding and faulting. Mineralized shoots are typically 4-15m thick, 50m-190m up/down-dip and 300-2,000m+ downplunge.

Mineralization at FGM occurs mainly as gold atoms trapped within the crystal lattice of disseminated arsenopyrite and pyrite (sulfides). These sulfide minerals precipitate in the wall rock sediments as selvage alteration proximal to veins that penetrate the host rock.

Arsenopyrite crystals occur as 0.05-6mm long acicular needles in random orientations. The disseminated pyrite associated with gold mineralization occurs as crystalline pyritohedrons 0.1- 2mm in size. Arsenopyrite is most important for the sulfide hosted gold mineralization (Roberts et al, 2003). Sulfide mineralization up to several meters occurs as selvedge alteration proximal to quartz-carbonate veining, and can be pervasive for hundreds of meters.

Visible gold has been observed in all areas of the underground workings at FGM and in some open cut pits within the MIN5404 lease.

Visible gold is observed within quartz-carbonate veins, with a noticeable increase in recent years as underground mining and diamond drilling has advanced deeper. Visible gold particles are predominantly specks (up to 3mm), however more rarely they can be > 5mm. The width of quartz- carbonate veining that contain visible gold is variable, with widths ranging from a few millimeters to several meters (true thickness). The veins usually have incomplete infill with druse quartz within those voids. Visible gold can be found as specks in narrow linear trends as well as isolated specks without a clear trend.

Alteration mineralogy associated with veins that host visible gold includes quartz-carbonate (ankerite), with minor occurrences of fibrous boulangerite (Pb5Sb4S11) as inclusions in euhedral quartz or as fibrous growths within void spaces. Clear to brown colored sphalerite (ZnS2) is also occasionally observed within veins. Selvage sulfide alteration can be present, proximal to veins hosting visible gold.

The visible gold has a spatial association with stibnite (Sb2S3). However, the stibnite mineralization can occur without visible gold (Henderson, 2014). The rationale for the one-way correlation is likely due to the stibnite mineralization occurring in different events, but utilizing the same structurally favorable locations. Stibnite mineralization is observed in all areas of the underground workings at FGM and has historically/previously been observed in some open cut pits within MIN5404.

At Fosterville sulfide gold mineralization is structurally controlled and localized by the discordant relationship between bedding and faulting. Gold mineralization is more continuous and of higher grades in fault zones where east-dipping beds occur adjacent to west-dipping footwall beds across faulting, such as along the Phoenix Fault (Boucher et al, 2008a), i.e.: discordant- concordant structural setting (locally termed oblique/parallel or parallel/oblique). Mineralized shoots are typically 4-15m thick, 50m-190m up/down-dip and 300-2,000m+ down-plunge. Sulfide gold grades are relatively smoothly distributed with both extremely high values and extremely low values being uncommon.

There are four geometric bedding-fault relationships present at Fosterville, primarily created through the interaction of west-dipping faulting that links across fold closures, from an anticline in the west to a syncline in the east. The four bedding relationships across a fault are locally referred to as parallel/parallel, parallel/oblique, oblique/oblique and oblique/parallel structural settings.

The controls on visible gold mineralization are less well tested compared with sulfide-hosted gold, however, general observations suggest that visible gold is focused along reactivated faults where sulfide hosted gold mineralization is located. Visible gold is generally found in higher concentrations on faulting proximal to anticline hinges. The Eagle Zone has a fault (Audax Fault) with an orientation that is northeast striking, and moderately southeast dipping, which is significantly different to all other mineralized faults at FGM. It would appear that this orientation has a strong control on visible gold mineralization, however, this is yet to be tested in other areas within FGM. The Swan Fault also moderately dipping (45-60o) but to the southwest at an oblique angle to the well-known Fosterville Fault Zone faults such as Lower Phoenix (Benu) and Kestrel. These noticeably different fault orientations around the Swan Zone mineralization are likely to strongly influence the degree of observed visible gold.

Since the completion of the Harrier Open Cut Mine in early December 2007, the sole source of ore had been the underground operations until Q2 2011 when ore feed became available from a series of open pit cut backs on the Harrier Pit, John’s Pit and O'Dwyer's South Pit. Since the completion of O'Dwyer's South cut back in Q4 2012, the sole source of ore has been from the underground operations. The current Life of Mine (LOM) plan contains ore sourced from underground operations only.

The underground mine commenced declining in March 2006 with production first recorded in September 2006. Development and stoping have been conducted in the Phoenix, Falcon, Ellesmere, Kink, Vulture, Raven, Robin and Harrier ore bodies since that time. As at January 1, 2017 works are planned to continue in the Phoenix, Central, Harrier and Robin ore bodies. All areas are planned to be extracted using open stoping techniques with the application of Cemented Rock Fill (CRF) where applicable and practical. Selection of the specific mining method within the open stoping regime is based upon previous experience at the Fosterville Mine and expectations of ore zone geometry and geotechnical conditions. A standard level interval of 20 vertical meters can be applied across all mining areas. However, this can be varied as is required to maximize the extraction of the economic material. The Phoenix to 4240rl, Harrier below 4500rl, Central and Robin ore bodies are accessed from a footwall decline position while the Phoenix below 4240mRL and Harrier ore body above 4500mRL are accessed from the hangingwall.

Underground mining is conducted using a conventional fleet including jumbos, production drills, loaders, trucks and ancillary equipment. Current mining is undertaken as owner miner.

The crushing circuit has the capacity to operate 24 hours per day, 7 days/week, at the design availability of 80%.

Run of Mine (ROM) ore is reclaimed from stockpiles on the ROM pad and fed to a bin by front-end loader, blending the ore in the process. Ore is then fed to a 760mm x 1,372mm single toggle jaw crusher by a vibrating grizzly feeder and minus 90mm crushed ore is conveyed to a coarse ore open stockpile with reclaim tunnel providing feed to a SAG mill.

Dust suppression measures are installed at the ROM bin. The crusher discharge and conveyor transfer points both being fitted with dust collectors.

Crushed ore is fed at a controlled rate onto a conveyor feeding a 3,500kW SAG mill (~6.1m in diameter x 6.1m). The ore is ground to a P80 of 75µm in closed circuit with hydrocyclones to liberate sulfide minerals containing gold from the barren gangue minerals. The milling circuit is designed to operate 24 hours per day with a throughput of up to 120 dry tph.

Since the commissioning of the processing plant in 2004, all processing models for the mill have been based on actual plant performances. The processing budget takes into consideration the mining schedule (ore source location, tonnes to be mined and gold grade), and predicted sulfur grades to be processed.

The process plant incorporates the following unit operations:
- Single stage crushing with a primary jaw crusher;
- Open stockpile with reclaim tunnel;
- 20ft diameter by 20ft length Semi-autogenous grinding (SAG) mill;
- A gravity circuit to recover coarse gold from the grinding circuit recirculating load;
- Flotation circuit to produce a gold bearing sulfide mineral concentrate and a barren residue;
- 8ft diameter by 13ft length flotation concentrate regrind mill;
- A gravity circuit to recover coarse gold from the flotation concentrate with gravity circuit concentrate being direct smelted;
- A Bio-oxidation circuit consisting of ........