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.
Lithium-boron mineralisation is hosted within two sedimentary basins located four kilometres apart: South Basin (9 km2) and North Basin (20 km2). 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 3.4 million tonnes of lithium carbonate and 11.3 million tonnes of boric acid (393Mt at 0.9% Li2CO3 and 2.9% H3BO3) making it one of the largest lithium and boron deposits in North America. The Resource is open in most directions and is likely to increase in size with additional drilling.
The South Basin Resource has a high-grade Li-B zone of 65Mt at 1.0% Li2CO3 and 9.1% H3BO3 containing a total of 650,000 tonnes of lithium carbonate and 5.9 million tonnes of boric acid.
The deposit is amenable to low-cost open pit mining methods and simple acid leaching with low acid consumption. A simple and low-cost flow-sheet is proposed to produce lithium carbonate and boric acid on-site.
The results of acid-leach metallurgical test work 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.
The simple process route being evaluated is crushing, grinding and flotation followed by acid leaching. The process will allow for the on-site production of lithium carbonate/hydroxide and boric acid.
Acid is a major cost in the proposed flowsheet and the reduction in acid consumption has been a major focus of the work. Low acid consumption will have a significant positive effect on project economics.
Key findings from the recent testwork are:
- High grade Li-B rich mineralisation occurs in thick (20-30m), 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.
- The host rocks are dominated by the minerals searlesite (B-bearing), sepiolite (Li-bearing), K-feldspar, calcite and dolomite.
- Calcite and dolomite (carbonate minerals which would otherwise consume large amounts of 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 using sulphuric acid with high leach recoveries (98% for Li and 99% for B) and low acid consumption (296kg per tonne of ore).
This testwork strongly indicates that Rhyolite Ridge can become cost-competitive, major producer of lithium carbonate and boric acid with scalable production options.