The Siviour graphite deposit is a well-defined EM conductor anomaly, elongated ~3 km W–E and ~0.6 km wide, that was outlined during an EM survey flown in 2006–07 by Cameco Ltd in the search for uranium mineralisation. Follow-up drilling by Cameco included one cored hole, CRD0090, near the eastern extent of the conductor. This intersected graphite mineralisation (Paxtons prospect) commencing at 67.7 m, but the graphite was not tested at the time. Subsequent analyses in 2014, on the core sample lodged with the South Australia Drill Core Reference Library, returned 12.4 m at 8.1% Cg, with over 40% of the graphite concentrate having flake size >150 µm. In 2015 a drill traverse across the central portion of the EM anomaly intersected high-grade, coarse-flake graphite at depths of 26 to 55 m below surface. Resource definition drilling by Renascor Resources Limited, during 2015–17, delineated a tabular, mostly flat-lying, graphitic biotite–quartz–feldspar schist with abundant coarse flake graphite for a total resource of 80.6 Mt at 7.9% TGC, at cutoff grade 3% TGC, containing 6.4 Mt of graphite. The graphite ore zone averages 20 m thickness, at a depth of 10 to 25 m below surficial cover sediments and weathered calc-silicate bedrock capped by calcrete. The extent of graphite mineralisation was reassessed in early 2017 using a helicopter EM survey to confirm the overall flat-lying shape of the orebody and to locate near-surface extensions to mineralisation along strike.

The geometry of the Siviour Graphite Deposit is generally flat-lying, with thick, flat, gently folding graphite mineralisation sitting from within 5 to 15 metres of the surface. This orientation facilitates a single shallow mining design that can be mined by conventional open pit mining.

Pit optimizations were completed by mining engineer consultant Optima based on production scenarios for both the large-scale (1.65Mt per annum) and small-scale (200,000t per annum) plants. Twenty pit shells were identified for mine planning purposes.

A schedule was developed that progressively mines in stages commencing in the south-eastern portion of the orebody of the large-scale production case to permit mining of a higher-grade corridor in the southern portion of the orebody in the mine’s first year. In the small-scale case, mining commences in a separate high-grade zone located in the southern portion of the ore-body.

Over the thirty-year life of mine, approximately 94% of the ore processed is within the Probable Ore Reserve category.

There is significant opportunity to further optimize the mine plan by extending the pit boundary to include near-surface high-grade zones. In particular, the resource remains open along-strike in the eastern portion of the orebody, including the area between the north-eastern and south-eastern limbs.

The Siviour PFS considers the construction of a 1.65Mt per annum processing plant. In the optional staged approach, a smaller-scale 200,000t per annum processing plant is initially constructed, and in year four, a larger-scale 1.65Mt per annum plant commences operation along-side the 200,000t per annum plant, for a total processing capacity of 1.85Mt per annum.

The process plants for both the 1.65Mt and 200,000t per annum plant are designed to recover graphite concentrate by froth flotation. Ore from the mine will be crushed in stages, followed by grinding, flotation, filtering, sizing and drying, before being bagged and containerised for shipment .

Crushing
For the large-scale plant, crushing will occur in three stages. In the first stage, a feeder breaker will permit optimal blending of ore from the ROM pad prior to primary and secondary crushing from approximately 600mm to 20mm. Ore will then be conveyed to a crushed ore stockpile before being sent to a scrubber to remove excess clays and assist with tertiary crushing/size reduction. For the small-scale plant, a mobile crusher will convey to a washing screen before milling; upon the completion of the larger plant in year four, the small-scale crushing circuit will be replaced by the large-scale crushing circuit, which is designed to accommodate 1.85Mt per annum.

Grinding
Crushed ore, containing both scrubber discharge and undersize material from a pebble crushing circuit screen, will be conveyed to a primary rod mill to achieve flotation feed of P80 500µm. The mill discharge will be collected in a hopper before being pumped to a cyclone cluster, with oversized material recycled back to the rod mill.

Flotation and Regrind
Flotation and regrind circuits contain roughing, scavenging, six stages of cleaning and five stages of regrind. The cleaning circuit includes screening of concentrate to 150µm after the second cleaning, with the coarser flake material undergoing a light regrind, before a final stage of cleaning and filtration and drying, the finer material will pass through additional regrind and cleaning to increase purity. The circuit is designed to optimize coarse flake graphite
retention at a minimum purity of 94% C, with purities of a minimum of 96% C targeted for finer flake fractions.

Dewatering
The final concentrates will be pumped into a thickener and then filtered, dried and screened into five size fractions (+300µm, +180µm, +150µm, +75µm and -75µm). Concentrates will then be directed to a hopper and bagged into one tonne bulka bags by product specification.

Tailings
Tailings, including slimes and flotation circuit tailings, will be directed to a tailings thickener for dewatering prior to being pumped to the tailings storage facility. Tailings thickener overflow will report to a process water tank for water recovery and reuse.