- Results from the 2nd stage of the current metallurgical program show that flotation is highly effective in removing carbonate minerals (calcite and dolomite) from the Li-B mineralisation.
- 58-65% of the carbonate was removed with Li and B recoveries >95%. Higher rates of carbonate removal (up to 81%) can be achieved at lower Li-B recoveries.
- The results show that the carbonate content of the Li-B mineralisation can be reduced from 11% CO3 to between 2.1 and 4.7% CO3 through carbonate flotation.
- Carbonate minerals consume acid and their removal prior to acid leaching will significantly reduce the amount of acid required to leach lithium and boron.
- Metallurgical results to date continue to support potential for a simple, low-cost acid leaching flowsheet using established technologies/processes.
- The 3rd stage of the current program is currently underway and involves acid leaching of the flotation concentrate to determine metal recoveries and acid consumption.
Global's Managing Director, Bernard Rowe commented: "We are very pleased with the flotation results as they clearly demonstrate that we can remove a large amount of the carbonate prior to the acid leach step and that will significantly reduce the amount of acid required to leach the lithium and boron from the rock. Importantly, very little lithium and boron are lost in the flotation process with recoveries greater than 95%."
The current metallurgical program is aimed at evaluating a simple process route involving crushing, grinding and flotation followed by acid leaching to recover lithium and boron. The relatively simple process route, using established technologies, is expected to compare favourably to other sources of lithium including brine and spodumene deposits.
Key steps in the current metallurgical program are to establish parameters for:
1. Crushing and grinding to liberate the mainly coarse-grained minerals - searlesite, k-feldspar, calcite, dolomite
2. Flotation to remove carbonate minerals (calcite, dolomite) Carbonate minerals consume acid but do not contain Li or B.
3. Acid leaching of the flotation concentrate (carbonate removed) to determine Li/B recoveries and acid consumption
Metallurgical testwork is being undertaken by Hazen Research in Colorado, USA and SGS Minerals in Ontario, Canada. The latest results are from a sample of Li-B mineralisation collected from outcrop from within the South Basin Mineral Resource and are considered to be representative of the high-grade Li-B searlesite mineralisation.
Reverse flotation was adopted to separate carbonate minerals (calcite, dolomite) from the lithium/boron bearing minerals. The head samples were crushed and ground in a rod mill at 62% solids, de-slimed by decantation (P80 of 133 microns after de-sliming), preconditioned with a fatty acid collector and rougher carbonate flotation was conducted. Two tests were conducted on the same sample using two different collector chemicals. The carbonate removed by flotation was 58-65% of the original feed in 14-17% weight mass.
Lithium and Boron recovered in the tailings and slimes were 96% and 95% respectively. The removal of carbonate gangue had a concentrating effect for lithium that was upgraded to a factor up to 1.7 in the slimes fraction.
The work done to date by Hazen Research compares well with the previous testing conducted by SGS in 2012 on this deposit where calcite flotation removed between 63% and 81% of the CaO depending on the desired mass pull and the associated lithium losses.
About Rhyolite Ridge Lithium-Boron Project
Rhyolite Ridge is a lithium-boron deposit located in southern Nevada. The deposit contains a Resource of 3.4 million tonnes of lithium carbonate and 11.3 million tonnes of boric acid, 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. In addition, the North Basin hosts lithium-boron mineralisation drilled by a previous exploration company in the 1980's that is not included in the Resource.
The Resource contains a high-grade Li-B zone referred to as the Searlesite Zone and comprising 65Mt at 1.0% Li2CO3 and 9.1% H3BO3 for a total of 650,000 tonnes of lithium carbonate and 5.9 million tonnes of boric acid - sufficient material to support a 3Mtpa mining operation over 20 years.
The mineralisation is hosted within shallow, flat-lying sedimentary rocks, representing a potential third source of lithium - in addition to brine and pegmatite types. Lithium-boron mineralisation occurs with the mineral searlesite - an acid leachable sodium boro-silicate mineral.
Rhyolite Ridge is located close to existing infrastructure and is 25km west of Albermarle's Silver Peak lithium mine and 340km by paved road from the Tesla Gigafactory. It has the potential to be a strategic, long-life, low-cost and reliable source of lithium and boron. Global has the exclusive right to purchase 100% interest in the project.
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About Global Geoscience Limited
Global Geoscience Limited (ASX:GSC) is a Sydney-based mineral exploration company specialising in greenfield exploration and mineral discovery. The Company's main focus is for copper, gold and silver on its mostly 100%-owned projects in Nevada and Arizona in the United States, and Peru in South America.
Global Geoscience Ltd
Cygnet Capital Pty Limited
Global Geoscience Limited (ASX:GSC) Drilling Underway at Rhyolite Ridge Lithium-Boron Project in Nevada