The Rhyolite Ridge deposit is amenable to low-cost, open-pit mining methods using excavators and trucks.
The orebody outcrops over 3 kilometres along the western margin of the South Basin and generally dips gently to the east. The thick (>20m) lithium-boron (Searlesite) mineralisation is very consistent along strike and down dip.
Mining will target shallow high-grade ore in the southwest portion of the resource to provide significant early cash flow.
The lithium-only (clay) mineralisation will be stockpiled near the quarry for potential future processing as it requires different processing than the lithium-boron (Searlesite) ore. The overburden storage area will also be located immediately west of the quarry.
Lithium carbonate and boric acid will be produced at Rhyolite Ridge using well-proven conventional processing technology.
In the Rhyolite Ridge PFS, ore is trucked to the processing area located 2 km northwest of the open pit where it will be:
- Crushed to 1-inch (25mm) and conveyed to a series of large concrete vats
- Leached with dilute sulphuric acid to recover nearly all of the lithium and boron into a Pregnant Leach Solution (“PLS”)
- Piped to the processing plant and the PLS will be cooled to separate boron first
- Boron-rich solution undergoes a series of evaporation and crystallisation steps in the boric acid plant and then purified into a boric acid product
- Lithium-rich solution undergoes a series of evaporation, precipitation and crystallisation steps in the lithium carbonate plant and then purified into a lithium carbonate product.
The waste rock from the vats will be washed and then dry stacked.
All of the sulfuric acid required for leaching will be produced by an on-site acid plant.
The acid plant will also produce:
- all of the steam required for evaporation
- all the power required on site
- a further 38MW of power available to be sold into the grid.
The schematic below shows the boric acid and lithium carbonate plant between the acid plant in the foreground and the vat leaching area in the background.
Overall recoveries are estimated to be 81.8% for the lithium and 83.5% for the boron.
The video below provides an overview of the mine and processing plant at Rhyolite Ridge: