Conventional open pit mining is proposed for the delivery of 100 000 t/month or 1.2 Mtpa of RoM material to the communition and processing facilities. In order to develop the pit design for the Arcadia deposit, an optimised pit shell was first prepared using Dassault System Surpac© software. The mining method is based on six nested sequential open pits (1a, 1b, 2, 3, 4 and 5). The final pit, (5) will measure some 1.1 km by 750 m, with a maximum depth of 130 m on the final high-wall. The total surface area of the final pit 5 will be approximately 0.55 km2.
Mining is anticipated to commence from the location of the historical open pit where the Main Pegmatite is exposed (Figure 5 and 6). Pit slope parameters were designed based on recommendations made by Geotechnical Consultants (Practara) with overall slope angles planned to be 54º - 56º, with a batter angle of 80º. 10 m high benches are planned, with an operating berm width of 15 m, and a final width of 5 m.
The pit design has also taken cognisance of the local resource geometry to maximise the location of the ramp with respect to pit entry location, pit base access and utilisation of the pit floor for access to the final benches. Waste dumps have been located as close as possible to the pit exit points to minimise haulage profiles without disrupting the access to the orebodies or crushing plant.
Mining operations will be conducted utilising a contracted fleet for key equipment with some ancillary vehicles being supplied by the Company. Ore and waste will be handled by diesel hydraulic excavators and articulated dump trucks. Ore will be trucked to the crushing station where it will be directly dumped to the primary crusher, or stockpiled prior to front-end loader feeding. Waste material comprising meta basalt and some pegmatites will require blasting except for some of the very upper weathered rocks.
The mining dilution was estimated at 5 %, and the total ore losses have also been estimated at 5 %. This is to take into account the fact that some waste material will be added into the ore stream going to the processing plant and that some of the ore material will be directed to the waste dump. The grade of the dilution material, added to the ore stream is taken to have an average value of 0 % Li2O. This conservative approach does not make any allowance for Li2O values which are likely to be contained in the dilutant material. This scenario maximises the recovery of ore during mining, hence the mining recovery of the open pit minable resource is considered to be 95 %.