- Metallurgical results continue to support potential for a simple, low-cost acid leaching flowsheet using established technologies and processes to produce lithium carbonate and boric acid on site.
- Testwork shows that flotation is highly effective in removing carbonate minerals (calcite and dolomite) from the Li-B mineralisation whilst maintaining high (>95%) recoveries of both metals.
- The lithium-boron flotation concentrate with low-carbonate content represents an ideal feed for acid leaching
- Acid leach tests have been completed on the flotation concentrate and results are imminent.
- Drill results at South Basin extend Li-B mineralisation for a further 200m to the east of the Resource
- North Basin drilling confirms thick, shallow zones of lithium-boron mineralisation
Rhyolite Ridge Lithium-Boron Project, Nevada
Rhyolite Ridge is a lithium-boron deposit located in southern Nevada, close to existing infrastructure. 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. Global Geoscience holds an exclusive option to purchase 100% interest in the project with no royalties to the owners.
Mineralisation is hosted by sedimentary rocks, representing a potential third source of lithium - in addition to brine and pegmatite types. The mineralised sedimentary rocks are thick, shallow and flat lying, making them ideally suited to open pit mining methods. The deposit has potential for simple, low-cost processing to produce lithium carbonate and boric acid. The relatively simple process route, involving crushing, grinding, flotation and acid leaching, is expected to compare favourably on a cost basis to other sources of lithium.
The project consists of two sedimentary basins (North and South) located four kilometres apart. South Basin (9km2) contains a Resource of 3.4 million tonnes of lithium carbonate and 11.3 million tonnes of boric acid. The Resource is open in three directions and is likely to increase in size with additional drilling. North Basin (20km2) contains thick, shallow zones of lithium-boron mineralisation intersected in wide-spaced historic drilling, but no resource has been estimated to date.
The South Basin Resource contains a high-grade Li-B zone of 65Mt at 1.0% Li2CO3 (1910 ppm Li) and 9.1% H3BO3 (1.6% B) for a total of 650,000 tonnes of lithium carbonate and 5.9 million tonnes of boric acid. The high-grade mineralisation is dominated by the mineral searlesite (>40% by weight), averages 20 metres thickness over an area of approximately two square kilometres. The high-grade zone outcrops along the western margin of South Basin.
The current metallurgical program is evaluating a simple process route involving crushing, grinding and flotation followed by acid leaching to extract lithium and boron in order to produce lithium carbonate and boric acid.
Key findings from the testwork completed to date are:
- Lithium and boron are contained in acid soluble minerals including searlesite and sepiolite and can be readily leached using dilute sulphuric acid (20%).
- High grade Li-B rich mineralisation occurs in thick (>20m), consistent and well defined sedimentary layers within the deposit where the mineral searlesite, a sodium borosilicate mineral, accounts for over 40% of the rock (by weight).
- Lithium-boron mineralisation occurs in relatively coarse grained rocks dominated by the minerals searlesite (B-bearing), K-feldspar, calcite/dolomite and sepiolite (Li-bearing)
- Calcite and dolomite (carbonate minerals) consume large amounts of acid during the leaching process but are able to be removed prior to leaching via simple flotation. 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%.
Acid leach tests have been completed on flotation concentrate (carbonate removed) and the results are imminent.
For further information regarding metallurgical testwork, refer to the following reports that are available to view on the Global Geoscience website:
"Metallurgy and Drilling Update Nevada Lithium-Boron Project" dated 23/01/2017
"Metallurgy Update Nevada Lithium-Boron Project" dated 9/03/2017
Five diamond core holes were completed during the quarter (3 at South Basin and 2 at North Basin) for a total of 1247m. Assay results have been received for all five holes. The results show that both North and South basins host thick zones of lithium-boron mineralisation over broad areas and that mineralisation remains open in most directions. The current Resource of 3.4 million tonnes of lithium carbonate and 11.3 million tonnes of boric acid will increase in size with the latest and additional drilling.
Three holes drilled at South Basin extended the Li-B mineralisation an additional 200m to the east of the Resource. All three holes were outside the current South Basin Resource and two of the three intersected lithium-boron mineralisation of similar grade and thickness to nearby holes. One hole (SLB-1) was abandoned before reaching target depth.
Highlights of the South Basin drilling were:
- 18.6m at 2148ppm Li and 1.33% B from 281.9m in SLB-2 (upper Li-B zone)
- 22.9m at 1354ppm Li and 1.68% B from 364.8m in SLB-2 (lower Li-B zone)
- 10.5m at 2213ppm Li and 0.63% B from 127.0m in SLB-3 (upper Li-B zone)
Two holes drilled at North Basin confirmed Li-B mineralisation previously identified and drilled by US Borax in the 1980's. Highlights of the North Basin drilling were:
- 67.0m at 1212ppm Li and 0.49% B from 22.9m in NLB-1
- 28.6m at 1517ppm Li and 0.40% B from 3.4m in NLB-2
Refer to Figure 2 (see the link below) on page 6 and Tables 1 and 2 on page 7 (see the link below) for further information regarding the drilling.
June Quarter Work Program
The June quarter work program will continue focus on work required for a pre-feasibility study including:
- Completion of acid leach testwork
- Optimisation of flotation and acid-leach process steps
- Production of a lithium-boron brine for crystallisation testwork
- Infill drilling (200m spacing) to upgrade the high-grade Li-B Resource to Measured category.
- Upgrading of the Resource estimation
- Commencement of pre-feasibility work
The Company welcomed Mr James D Calaway to the board of directors as non-executive chairman. Mr. Calaway is a respected business and civic leader residing in Houston, Texas, with considerable experience and success in building junior companies into successful commercial enterprises. He has played major roles in the development of both public and private companies engaged in lithium operations, oil and gas exploration and production, enterprise software and solar farm development.
Until his retirement in July 2016, Mr. Calaway served for eight years as non-executive Chairman of the Board of Orocobre Ltd, (ASX:ORE) (TSE:ORL), helping lead the company from its earliest development to becoming a significant producer of lithium carbonate and a member of the ASX 300. With Orocobre being the only other lithium company with a significant exposure to boron, his Orocobre experience ideally suits him to help lead Global to become a leader in the lithium and borates businesses.
As a condition of the appointment of Mr Calaway, the company completed a $5.2m (US$4m) share placement to entities controlled by and related to Mr Calaway.
During the March quarter, the Company spent $827,000 on exploration and $380,000 on corporate/administration/salaries. Current cash on hand (post-placement) is $8 million.
To view tables and figures, please visit:
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 Limited