The Greenbushes pegmatite deposit consists of a primary pegmatite intrusion with numerous smaller, generally linear pegmatite dikes and pods to the east. The primary intrusion and its subsidiary dikes and pods are concentrated within shear zones on the boundaries of granofels, ultramafic schists and amphibolites. The pegmatites are crosscut by ferrous-rich, mafic dolerite which is of paramount importance to the current mining methods. The pegmatite body is over 3 km long (north by northwest), up to 300 m wide (normal to dip), strikes north to north-west and dips moderately to steeply west to south-west. The syn-tectonic development of the pegmatite has given rise to mylonitic fabrics, particularly along host rock contacts.

The Greenbushes pegmatite is mineralogically segregated into five primary zones. Internally, the Greenbushes pegmatite consists of the Contact Zone, Potassium Feldspar (Potassium) Zone, Albite (Sodium) Zone, Mixed Zone and Spodumene (Lithium) Zone. The zones differ from many other rare-metal pegmatites in that they do not appear concentric, but are lenticular in nature, with inter-fingering along strike and down dip. They do not have a quartz core. The mine sequence was later subjected to the transgressive east-west dike and conformable sill dolerite intrusions.

The highest concentrations of primary ore minerals are found in specific mineralogical zones or assemblages within the pegmatite. The high-grade lodes within the main pegmatite body exhibit variable dips from 80 to 20° towards the west and south-west. Tantalum (tantalite) and tin (cassiterite) mineralization is concentrated in the Sodium Zone which is characterized by albite (Na-plagioclase), tourmaline and mica (muscovite). The Lithium Zone is enriched in the lithium bearing silicate spodumene. The mixed zone contains lower concentrations of tantalum and lithium. The final major zone is the potassium feldspar microcline which is not as economically important.

In general, the hanging wall to the pegmatite bodies is composed of amphibolite (meta-basalt and sub-volcanic intrusive bodies) whereas the footwall is granofels, dominantly of metasedimentary origin. The amphibolites and dolerites contain occasional stringers and pods of sulphides such as pyrite, pyrrhotite and chalcopyrite. Arsenopyrite and arsenolamprite (native arsenic) are noted in some areas, particularly within granofels and amphibolite inliers in the main pegmatite. Accessory minerals in the pegmatite are apatite and small amounts of beryl and garnet. Waste rocks are not as well-logged or understood at the same level of detail as the pegmatites in general.

Weathering and erosion of the pegmatites has produced adjacent alluvial deposits in ancient drainage systems. These are generally enriched in cassiterite. All rocks have been extensively lateritized during Tertiary peneplain formation; the laterite profile locally reaches depths in excess of 40 m below the original surface.

The C3 Pit contains the main lithium deposit. The lithium ore deposit occurs within a large (250 m wide) lithium enriched pegmatite. Spodumene in the Lithium ore zone can make up more than 50% of the rock with the remainder being largely quartz. Toward the northern end of C3 pit, a highly felspathic (K-feldspar) zone separates the high-grade lithium zone from the hanging wall amphibolite and the dolerite sill. Tantalum/tin and lithium ore body mineralization are conformable with the trends of the pegmatites both along strike and down dip.

Between C3 and C1 is the mining area referred to as C2. The pegmatite in this area dips approximately 40° west and has an intermediate composition with moderate lithium oxide Li2O values and moderate tantalum pentoxide (Ta2O5) values. This is in contrast to C1 and C3 which have large distinct zones of separate Li2O and Ta2O5 high grade.

At the southern end of the Central Lode pits is the C1 pit area. It contains the next largest concentration of high grade spodumene lithium mineralization after C3. The eastern footwall contact in the south of the C1 area dips 35 degrees west steepening toward the north and with depth. The internal grade domains in C1 parallel the eastern footwall contact. The immediate footwall is enriched in tantalum with typical accessory minerals tourmaline and apatite visible. Above are zones of lithium mineralization crosscut by deep weathering near surface altering the pegmatite to kaolin. Moving north the dip of the pegmatite shallows and the lithium domain at more than 1% Li2O is discontinuous.

Mineralogy
As stated above, internally the Greenbushes pegmatite displays up to five mineralogically defined zones; the Contact Zone, K-Feldspar (Potassium) Zone, Albite (Sodium) Zone, Mixed Zone and Spodumene (Lithium) Zone. Zones generally relate to multiple phases of intrusion and crystallization of the pegmatites.

The zones occur as a series of thick layers commonly with a lithium zone on the hanging wall or footwall, K-feldspar towards the hanging wall and a number of central albite zones. High-grade tantalum mineralization (more than 420 grams per tonne [g/t]) is generally confined to the Albite zone within the deposit. The Spodumene and K-Feldspar Zones typically have tantalum-tin grades of less than 100 ppm.

Major minerals are quartz, spodumene, albite and K-feldspar. Primary lithium minerals are spodumene, LiAlSi2O6 (~8% Li2O) and spodumene varieties kunzite and hiddenite. Minor lithium minerals include lepidolite (mica), amblygonite and lithiophilite (phosphates). Spodumene is hard (6.5-7) with an SG of 3.1-3.2. Highest concentrations (50%) of Spodumene occur in the C1 and C3 pits.

When spodumene is weathered and oxidized the lithium ions leach into the environment, the result is spodumene pegmatite weathered to clay. This is of little to no economic value to the current operation. Oxidation of the pegmatites has generally occurred in near-surface weathering or along selected structures internal to the pegmatites. Only the near-surface weathering is considered to materially affect the pegmatite from a process mineralogy standpoint.

Deposit Geometry
The Central Lode pegmatite deposit extends over a strike length of 3.5km north-south (local mine grid) and has previously been sub-divided for practical purposes into four sectors representing past and present open pit operations, known as (from north to south) the Cornwall (tantalum only), C3, C2 and C1 pits.

However, recent drilling has demonstrated broad continuity at depth over the entire strike length and it can be considered as a single entity for resource and reserve modeling purposes. The overall pegmatite zone dips grid west at approximately 40º, has an overall thickness approaching 300m, and has been interpreted to a depth of over 600m below surface.

The Kapanga deposit lies some 300m east of Central Lode. It has been interpreted over 1.8km of strike and trends sub-parallel to Central Lode, dipping typically at 40-50º to the west-southwest, but steepening to 60º in the south. It comprises several stacked sub-parallel lodes of varying thicknesses, as well as smaller pods, with an overall thickness of approximately 150m, including intervening wallrocks. Mineralised pegmatite has been intersected by drilling to a depth of 450m below surface.

Current mining at Greenbushes is based on open pit extraction using conventional hydraulic excavators and haul trucks; mining is at a rate of approximately 4.5 million bank cubic meters per annum (“Mbcmpa”). The mining activities of load and haul are carried out by mining contractor, SG Mining Pty Ltd (“SGM”), and drill and blast activities are contracted to Action Drill and Blast Pty Ltd (“ADB”); Talison provides grade control and overall pit management.

Historically there was underground and open pit mining at Greenbushes, but the mineral reserves and LoM plan are based only on open pit mining.

Open cut mining of lithium ore is currently from the Central Lode open pits, south of the Cornwall Pit. The higher grade lithium ore is mined from a distinct zone within the pegmatite on the hanging wall side of the C3 (North) zone and from the large zone within the C1 (South) zone.

The mining plan involves a series of stages, including eastern and western cutbacks of the C1 and C3 pits. The eastern cutback of C3 pit, which has commenced, is in two parts, Central and East, with the Central cutback of the east wall being taken down initially before moving to the southern wall and taking out the saddle between the C3 and C1 pits, within the area referred to as the C2 pit. During the 21-year period scheduled, the overall Central pit will have a number of staged cutbacks involving both the east and west walls as well as the mining of the Kapanga pit to the east of the C1 pit.

The existing Central pit area extends around 2,000m north-south with C3 pit being around 700m east-west and C1 being around 350m east-west. Kapanga pit extends approximately 1,300m north-south and 700m east-west. C3 pit bottom is currently at 1150mRL (around 175m deep) and C1 pit bottom is at 1180mRL (around 85m deep). Final pit floor at completion of the current mine design is 870mRL in C3 pit and 1120mRL in C1 pit, with the final depth of the pit at 455m. The Kapanga final pit is 1012mRL, around 300m deep.

Pit Optimisation and Designs
The geotechnical parameters used in the 2021 optimisation were drawn from recommendations from geotechnical consultant, PSM Consult Pty Ltd (“PSM”). Allowances for haul road segments were included in the design parameters. The designs are consistent with current operating practices for the Central Lode pits. Ramp width was set at 18m single lane and 26m for two-way traffic. Haul road gradient was set at 1:10 or approximately 6º. The final C3 pit floor is at 870mRL, with a high wall of approximately 455m; the final C1 pit floor is at 1120mRL, with a high wall of approximately 160m and the final Kapanga pit floor is at 1012mRL, with a high wall of approximately 300m. The east wall of Kapanga will require some of the Floyd’s waste dump to be cut back to provide sufficient distance between the pit limit and the toe of the waste dump.

The final reserve pit has been designed with 20m bench heights, with 8 to 8.5m bench widths and overall wall angles between 37º and 44º in the west and between 25º and 34º in the east. Local batter angles vary with local ground conditions.

The voids of the former underground development within the open pit design in the Central Lode have not been extracted from the reserve but the size is estimated to be around 200kt which is not material to the estimation.

There is no distinctive pit floor at C2 pit; the pit provides access into the C3 pit.

The current waste dump design has a final slope angle of 12 to 13° overall. This is to support concurrent reclamation to final configuration.

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The site comprises a large open-pit mine, four processing plants – three producing chemical grade lithium concentrates: Chemical Grade Plant 1 (CGP1) and Chemical Grade Plant 2 (CGP2) and the Tailings Retreatment Plant (TRP), one producing technical grade lithium concentrates, Technical Grade Plant (TGP), and associated support infrastructure.

The combined product from TGP, CGP1, CGP 2 and TRP will produce around 1.5Mt of lithium concentrate.

Tailings Retreatment Plant (Construction completed in 2022)
The TRP is an oxide flotation plant and is designed to reprocess 2Mtpa of old tantalum processing tailings from Tailings Storage Facility 1, which has an average spodumene grade of 1.4% Li2O. Nominal production from the TRP is expected to be 280ktpa for a period of five years, with nameplate capacity expected to be reached in FY23.

Technical Grade Plant
TGP is a relatively small plant that processes approximately 350,000 t/y of ore at an aver ........