Rhyolite Ridge Lithium-Boron Project
Global Geoscience’s 100%-owned Rhyolite Ridge project is a large, shallow lithium-boron deposit located close to existing infrastructure in southern Nevada. The project lies 25km west of Albermarle’s Silver Peak lithium mine and 340km from the Tesla Gigafactory near Reno.
Rhyolite Ridge is one of the largest lithium and boron deposits in North America and has the potential to become a strategic, long-life and low-cost source of lithium and boron.
The outcropping deposit is amenable to open pit mining at low strip ratios. High-grade lithium-boron mineralisation is the focus of the Rhyolite Ridge Pre-Feasibility Study (”PFS”) as it represents potentially the highest value material combined with a low-cost, simple processing route. This is due to the low-clay, low-carbonate and high-searlesite content of the rock, which make the mineralisation amenable to low-cost acid leaching at ambient temperature and pressure.
Geology and Mineral Resources
Lithium-boron mineralisation is hosted within two sedimentary basins located four kilometres apart: South Basin (9 km²) and North Basin (20 km²). The minerals in the host rocks are dominated by the searlesite (boron-bearing), sepiolite (lithium-bearing), K-feldspar, calcite and dolomite.
At South Basin, high-grade lithium-boron mineralisation occurs in 20m to 50m thick, sub-horizontal sedimentary layers. The upper-most layer is 20 to 30m thick and outcrops along the western margin of South Basin over a strike length of approximately 3km.
Drilling at South Basin has defined an Indicated and Inferred Resource of 460 million tonnes at 0.9% Li2CO3 and 2.6% H3BO3), containing 4.1 million tonnes of lithium carbonate and 11.9 million tonnes of boric acid. The Resource is open in most directions and is likely to increase in size with additional drilling.
The Mineral Resource includes a high-grade lithium-boron zone of 137Mt at 0.9% Li2CO3 and 7.2% H3BO3, with 75% in the Indicated category.
Global Geoscience is conducting metallurgical testwork to establish the process flowsheet.
Metallurgical testwork announced in May 2017 confirmed the potential for a simple, low-cost acid-leach process to produce lithium carbonate and boric acid at Rhyolite Ridge. This testwork focused on a flowsheet involving crushing, grinding and flotation followed by agitation (tank) leaching. Due to the high recoveries obtained, a number of other potentially lower cost (capital and/or operating costs) acid leach options are being evaluated.
Key findings from the recent testwork are:
- High grade lithium-boron rich mineralisation occurs in thick (20-50m), consistent and flat lying sedimentary layers within the deposit. Mineralogical and geochemical continuity is very high across the deposit including between outcrop and at depth in drill core.
- Calcite and dolomite (carbonate minerals which would otherwise consume acid during the leaching process) can be removed via flotation prior to leaching. The carbonate minerals are floated off while the boron and lithium bearing minerals sink and report to the flotation tailings. Flotation recoveries for lithium and boron are above 95%.
- Lithium and boron can be leached at ambient temperature and pressure using sulphuric acid with high recoveries and low acid consumption.
This testwork strongly indicates that Rhyolite Ridge can become cost-competitive, major producer of lithium carbonate and boric acid with scalable production options.