The Kathleen Valley Lithium Project is located on the western edge of the Norseman-Wiluna Greenstone Belt within the Archaean Yilgarn Craton of Western Australia. The belt consists of mafic and ultramafic volcanics with considerable volumes of clastic sediments, minor felsic volcanics and differentiate gabbros. The greenstones in the Kathleen Valley area have been metamorphosed to upper greenschist-lower amphibolite facies metamorphic grades and include tholeiitic lavas, differentiated gabbroic sills and ultramafic chlorite schists.

Lithium mineralisation is hosted within spodumene-bearing pegmatites, which are part of a series of lithium-caesium-tantalum (LCT)-type rare metal pegmatites that intrude mafic and sedimentary rocks in the region.

Twenty mineralised pegmatites have been identified at the Kathleen Valley Project hosted by two, outcropping, NW/SE trending pegmatite swarms – a shallowly-dipping, north-eastern swarm (Kathleen’s Corner), which contains approximately 90% of the pegmatites, and a steeper dipping south-western swarm (Mt Mann). The two swarms are interpreted to merge at depth to form a single, thick, moderately dipping mineralised body which remains open down-dip and along strike.

Most of the lithium is contained within spodumene. Small, isolated zones of petalite mineralisation has been observed (this material equates to <0.5% of the resource samples) in the north-western part of the deposit.

The mineralisation is contained within pegmatite veins that are readily distinguished from the surrounding rocks. Sectional interpretation and wireframing indicates good continuity of the interpreted pegmatite veins both on-section and between sections. The confidence in the grade and geological continuity is reflected by the assigned resource classification.

The mineralisation at Kathleen Valley extends from surface and would be suitable for open pit mining. High grade mineralisation is present at depth and would be suitable for underground mining.

Open Pit
Conventional open pit mining using excavators and rigid dump trucks was selected as the preferred mining method. Experienced mining contractors will undertake all aspects of the mining operation. Supervision, grade control and planning will be undertaken by an Owner’s team. All material will be blasted. Bulk waste will be blasted on 12m benches and the ore zones will be blasted on 6m benches and mined in two or three flitches for greater selectivity (depending on the point in the mine schedule) with ore delivered to blend fingers on the ROM pad.

Oxidation is shallow from 5-20 m in depth with slope angles of ~50o on the hanging wall and ~37 o on the footwall. Overall slope angles in fresh material were ~57 o on the hanging wall and ~45 o on the footwall. As the Kathleen Valley orebody dips at substantially less than wall angle constraints, the pit shells are optimally shallower than these angles to the south-west. An allowance for Grade Control drilling was made based on a dedicated RC drilling program at 24 m vertical intervals.

The open pit has been designed in two phases, the first being to supply ore for the plant in the first 3 – 4 years until the underground operation is up to full capacity. The second phase occurs after 25 years when the UG mining operation is winding down. The open pit designs contain a total of 30Mt of ore, at a diluted grade of 1.2% Li2O/ 135ppm Ta2O5. The pits contain 253 Mt of waste material foran average strip ratio of 8.4:1. Importantly in the first 10 years of production the stripping ratio is significantly lower than the previous PFS which had an average strip ratio of 12:1. Open pit mining dilution was applied using an edge of 0.5 m to a Selective Mining Unit (SMU) block size of 5m x 5m x 2m in the early open pit mining phase and 5m x 5m x 3m in final open pit phase.

Underground
There are two distinct mining areas in the underground mine. The Mt Mann mining area consists of steeply dipping ore domains, while the North-West Lodes mining area consists of shallowly dipping, stacked ore lodes. Mining methods have been selected based on the dip, width and geotechnical characteristics of the orebodies.

The Mt Mann mining area will be mined using transverse retreat open stoping in panels, as either single lift (30m stope height), or double lift (60m stope height). Stopes will be mined in a primarysecondary, bottom up sequence, within the stoping panel (generally 4 stopes high). The overall mining sequence will be bottom-up. Primary stopes will be filled with Cemented Paste Backfill (CPB) to maintain geotechnical stability and maximise ore recovery.

The Mt Mann mining sequence is bottom up within each stoping panel, generally four stopes high. The overall sequence is top down. Stopes will be mined in a primary-secondary sequence. The lower 15m of the bottom stope of each panel will be filled with a higher strength CPB (8% rather than the standard 4%), to maintain geotechnical stability when the lower panel is mined underneath. Stopes will be mined from footwall to hangingwall, to avoid undercutting previously filled CPB stopes. Where practicable, in the secondary stopes, rock filling has been utilized to minimize waste haulage to surface.

The North-West lodes will be mined using:
• Longitudinal retreat open stoping, where orebody width is greater than 10m. These stopes will be mined in a primary-secondary, bottom up sequence. Stopes will be filled with CPB to maintain geotechnical stability and maximise ore recovery.
• Room and pillar mining, where orebody width is between 5m and 10m. Ore recovery is lower for this method due to the ore pillars left behind to maintain room stability. Back filling will not be carried out in the room and pillar mining areas.

In the North-West Lodes, the mining sequence for the open stopes is similarly bottom up, with CPB used to maintain geotechnical stability. The Room and Pillar stopes will also be mined bottom up, but will not be filled. The use of fill in the open stopes avoids the need for pillars between stopes to maintain stope stability. Given the width of the orebody, appropriately sized pillars would significantly reduce the extraction percentage, and hence the economic viability of the orebodies. Stopes are sequenced to manage the open voids underground and maintain geotechnical stability.

Given the relatively shallow depth (around 440m below surface) of the underground portion of the mine, access via a surface portal and 1 in 7 decline, was decided upon as the most time and costeffective access option. An in-pit portal will also be utilised to access the southern end of the Mt Mann pegmatites. The decline will be mined in the footwall with a minimum stand-off from the orebody of 50m.

Mining recoveries of 95% were applied to all open stopes, and 90% for all room and pillar stopes, to account for ore within the stope shape that could not be extracted. This occurs primarily due to geometry issues of boggers navigating around 90-degree corners and being unable to fully reclaim all blasted ground. Due to the requirement to leave behind ore pillars in the Roomand Pillar stopes, mining recovery is further reduced from operational mining recovery, to 84% for the 5m-7m wide stopes, and 82% for the 7m-10m wide stopes. Mining recoveries of 100% were applied to all development, with the expectation that development headings could be bogged clean.

The underground designs contain a total of 49 Mt of ore, at a diluted grade of 1.50% Li2O/ 125ppm Ta2O5. Underground mining dilution was applied in two ways; applications of Equivalent Linear Overbreak Slough (ELOS) skins of 0.5m to the designed stope shapes and factors were applied to stopes that were likely to incur dilution from surrounding paste fill exposures, which varied from 1 to 4% depending upon the number of paste surfaces exposed by each stope for the vertical and flat zones respectively.

Experienced mining contractors will undertake all aspects of the mining operation using a mechanised mining fleet with truck haulage of ore from underground stoping panels via two portals to the surface ROM. Supervision, grade control and planning will be undertaken by an Owner’s team with ore delivered for further blending on the ROM pad.

The primary ventilation network consists of the two decline ramps and an intake shaft for intake air supply, and five exhaust shafts equipped with exhaust fans for primary exhaust. Inter-level exhaust raises will connect production areas with the main exhaust shafts. Air quantities have been calculated based on the expected equipment and personnel numbers and in line with WA Mining Regulations.

The process facilities include:
• Three-stage crushing (including HPGR);
• Low and high intensity magnetic separation combined with sequential gravity separation to produce a tantalum concentrate (also removes ferrous impurities);
• Ball-milling of the tantalum circuit non-magnetics

The Kathleen Valley Project process plant consists of a mineral processing concentrator with associated services and ancillaries. The plant has been designed using robust equipment and processes and significantly simplified following the adoption of WOF processing. The process facilities include:
• Three-stage crushing (including HPGR);
• Low and high intensity magnetic separation combined with sequential gravity separation to produce a tantalum concentrate (also removes ferrous impurities);
• Ball-milling of the tantalum circuit non-magnetics;
• Flotation thickening and filtration to produce Li2O concentrate; and
• Tails disposal.

In parallel with the PFS, a scoping level study (+/-30% Accuracy) has been initiated to review the integrated downstream processing of the Kathleen Valley product. The study has been carried out in parallel with the PFS.

The proposed downstream refinery flowsheet consists of either an LHM or LSM refinery with a ........