SYDNEY, Australia, Oct. 23, 2018 (GLOBE NEWSWIRE) -- Australian-based lithium-boron developer Global Geoscience Limited (“Global” or the “Company”) (ASX: GSC) is pleased to announce an updated Mineral Resource Estimate for its 100%-owned Rhyolite Ridge Lithium-Boron Project (“Rhyolite Ridge” or the “Project”) in Nevada, USA. 

The Indicated and Inferred Resource for the South Basin at Rhyolite Ridge is now estimated to total (at a 1,050ppm lithium cut-off):

• 475 million tonnes at 1,610 ppm lithium (equivalent to 0.9% lithium carbonate) and 4,100 ppm boron (equivalent to 2.3% boric acid)
• Containing 4.1 million tonnes of lithium carbonate and 10.9 million tonnes of boric acid

The Indicated and Inferred Resource includes a high-grade, lithium-boron portion now estimated to total (at a 1,050ppm Li and 0.5% B cut-off):

• 121 million tonnes at 1,740 ppm lithium (equivalent to 0.9% lithium carbonate) and 1.26% boron (equivalent to 7.1% boric acid)
• Containing 1.1 million tonnes of lithium carbonate and 8.6 million tonnes of boric acid

The 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 and high-searlesite content of the rock, which make the mineralisation amenable to low-cost acid leaching

The deposit is large, tabular, and moderately dipping. The defined dimensions are approximately 1,400 m x 2,500 m and are comprised of two ore zones approximately 20 m in thickness.

The Resource remains open to the north, south and east and has significant potential to expand with further drilling of the South Basin.  Not included in the Mineral Resource estimate is known lithium-boron mineralisation in the North Basin at Rhyolite Ridge.

The Mineral Resource was updated with a revised geological interpretation as a result of an alternative development strategy for the Project. This estimate is an update to a Mineral Resource estimate completed in October 2017 for the South Basin deposit. Previously, the high-grade lithium-boron component of the Resource was estimated at 137 million tonnes at 1,800 ppm lithium (equivalent to 0.9% lithium carbonate) and 1.26% boron (equivalent to 7.2% boric acid),

Boron is contained in the mineral searlesite (chemical formula NaBSi₂O₅(OH)₂) and lithium is tentatively attributed to lithium fixed in the mineral sepiolite (chemical formula Mg₄Si₆O15(OH)₂.6H₂O).

Drilling within the South Basin deposit extends to a vertical depth of approximately 405m and the mineralisation was modelled from surface to a depth of approximately 400m below surface.  The Mineral Resource estimate is based on good quality trench, RC and DD drilling data.  Drill hole spacing varies from approximately 200m by 200m in the well-defined portions of the deposit to 400m by 400m over the remaining areas.

Mineral Resource Statement and Parameters

October 2018 Mineral Resource Estimate (1,050ppm Li Cut-off)

Total Resource including Lithium-Only Mineralisation and Lithium-Boron (Searlesite) Mineralisation

October 2018 Mineral Resource Estimate (1,050ppm Li and 0.5% B Cut-Off)

Lithium-Boron (Searlesite) Mineralisation

Notes:

1. Totals may differ due to rounding, Mineral Resources reported on a dry in-situ basis.

2. The Statement of Estimates of Mineral Resources has been compiled by Mr. Robert Dennis who is a full-time employee of RPM and a Member of the AIG and AusIMM. Mr. Dennis has sufficient experience that is relevant to the style of mineralisation and type of deposit under consideration and to the activity that he has undertaken to qualify as a Competent Person as defined in the JORC Code (2012).

3. All Mineral Resources figures reported in the table above represent estimates at 11 July 2018. Mineral Resource estimates are not precise calculations, being dependent on the interpretation of limited information on the location, shape and continuity of the occurrence and on the available sampling results. The totals contained in the above table have been rounded to reflect the relative uncertainty of the estimate. Rounding may cause some computational discrepancies.

4. Mineral Resources are reported in accordance with the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (The Joint Ore Reserves Committee Code – JORC 2012 Edition).

5. Reporting cut-off grade selected based on an RPM cut-off calculator assuming an open pit mining method, a US$10,000/t Li2CO3 price, a 80% metallurgical recovery for Li2CO3 and costs derived from a high level technical report supplied by independent processing consultants to Global. Additionally a 0.5% B cut-off constraint was applied to report the portion of the Resource with potentially better processing characteristics and which according to current plans would be the initial portion of the Resource exploited.

Summary of Resource Estimate Parameters and Reporting Criteria

In accordance with ASX Listing Rules and the JORC Code (2012 Edition), a summary of the material information used to estimate the Mineral Resource is detailed below (for further information please refer to Table 1 in Appendix 1).

• The Rhyolite Ridge Mineral Resource area extends over a north-south strike length of 2,450m (from 4,184,000mN – 4,186,450mN), has a maximum width of 1,250m (424,150mE – 425,400mE) and includes the 420m vertical interval from 1,920mRL to 1,500mRL.
• The Rhyolite Ridge Project tenements (unpatented mining claims) are owned by Paradigm Minerals Arizona Corporation, a company wholly owned by Global Geoscience Ltd. The unpatented mining claims are located on US federal land administered by the Bureau of Land Management (BLM).

Geology and Geological Interpretation

• Lithium, boron and potassium mineralisation is stratiform in nature and is hosted within Tertiary-age carbonate-rich sedimentary rock, deposited in a lacustrine environment in the Basin and Range terrain of Nevada, USA.

Drilling Techniques and Hole Spacing

• Drill holes used in the Mineral Resource estimate included 19 trenches, 42 RC holes and 24 diamond holes for a total of 8,952m within the defined mineralisation.  The full database contained records for 85 drill holes for 15,802m of drilling and trenching. 
• All drill hole collars have been surveyed to the UTM Zone 11 NAD27 grid system.  For previous owners/operators, collars were survey by a contract surveyor utilising a GPS device.  Holes drilled by Global Geoscience were surveyed by DGPS.  Most of the earlier holes have now also been recently re-located and surveyed by DGPS unit in UTM Zone 11 NAD83 grid system.
• No down hole surveys were conducted for the trenches or RC holes, therefore nominal surveys were designated. Down hole survey methodology for the diamond drilling was not recorded, however readings were conducted on approximate 30m intervals down hole.
• Drill hole spacing is 200m by 200m (or less) over most of the deposit.  Spacing increases to approximately 200m by 300m along the eastern margin of the deposit.
• Drill holes were logged for a combination of geological and geotechnical attributes.  The core has been photographed and measured for RQD and core recovery. 

Sampling and Sub-Sampling Techniques

• Drilling was conducted by American Lithium Minerals Inc., the previous owner of the tenements between 2010 and 2011 and by Global Geoscience in 2017. For RC drilling, a 5 inch hammer with crossover-sub was used with sampling conducted on 1.52m intervals and split using a rig mounted rotary splitter. The hammer was replaced with a tri-cone bit in instances of high water flow. For diamond core, HQ core size diameter with standard tube was used.  Core recoveries of 97% were achieved at the project.  The core was sampled as half core at 1.52m intervals using a standard electric core saw.

Sampling Analysis Method

• Samples were submitted to ALS Chemex Laboratory in Reno, Nevada for sample preparation and analysis.  The entire sample was oven dried at 105˚ and crushed to -2 mm.  A sub-sample of the crushed material was then pulverised to better than 85% passing -75µm using a LM5 pulveriser.  The pulverised sample was split with multiple feed in a Jones riffle splitter until a 100-200g sub-sample was obtained for analysis.
• Analysis of the samples was conducted using aqua regia 2-acid and 4-acid digest for ICP-MS on a multi-element suite.  This method is appropriate for understanding sedimentary lithium deposits and is a total method.
• Standards for Li, B, Sr and As and blanks were routinely inserted into sample batches and acceptable levels of accuracy were reportedly obtained. Overall, QAQC results deemed all assay data suitable and fit for purpose in Mineral Resource estimation.

Cut-off Grades

• The Mineral Resource has been reported at a 1,050ppm lithium cut-off. The cut-off was selected based on an RPM cut-off calculator assuming an open pit mining method, a US$10,000/t Li₂CO₃ price, a 80% metallurgical recovery for Li₂CO₃ and costs derived from a high level technical report supplied by independent processing consultants to Global Geoscience and metallurgical test work results reported by Global Geoscience.  Within the 1,050ppm lithium cut-off domain a sub-domain set at a cut-off of 0.5% boron was reported to define a zone of lithium-boron rich mineralisation within the Mineral Resource.  The presence of boron associated with lithium is considered favourable as the mineralisation potentially has higher value and, based on studies by Global Geoscience, has potentially lower processing costs and capital requirements. 

Estimation Methodology

• Samples were composited to 1.525 m based on an analysis of sample lengths inside the wireframes. After review of the project statistics, it was determined that high grade cuts for B within most mineralised domains were necessary. The cuts applied ranged between 500ppm and 15,000ppm B, resulting in 100 B composites being cut.
• The block dimensions used in the model were 100m N-S by 50m E-W by 5m vertical with sub-cells of 6.25m by 6.25m by 1.25m.  This was selected as the optimal block size as a result of kriging neighbourhood analysis.
• Ordinary kriging grade interpolation was used for the estimate, constrained by Mineral Resource outlines based on mineralisation envelopes prepared using a nominal 1,000ppm Li cut-off grade with a minimum down-hole length of 3m. For internal high grade B zones, a nominal 5,000ppm B cut-off grade was used. Up to four passes were used to estimate the blocks in the model and more than 99% of blocks were filled in the first two passes.
• A total of 137 bulk density measurements were taken on core samples collected from diamond holes drilled at the Project using the water immersion technique.  Bulk densities ranging between 1.8t/m³ and 2.11t/m³ were assigned in the block model dependent on mineralisation and lithology. 

Classification Criteria

• The Mineral Resource was classified as Indicated and Inferred Mineral Resource based on data quality, sample spacing, and lode continuity.  The Indicated Mineral Resource was defined within areas of close spaced diamond and RC drilling of less than 200m by 200m, and where the continuity and predictability of the mineralised units was good.  The Inferred Mineral Resource was assigned to areas where drill hole spacing was greater than 200m by 200m and less than 400m by 400m.

Mining and Metallurgical Methods and Parameters

• Based on the relatively low angle dips, thicknesses and depths of the mineralised bodies that have been modelled, as well as their estimated grades, the potential extraction method is considered to be open pit mining.
• There are two types of mineralisation present: 1) lithium-boron mineralisation that is low in clay content and low-moderate in carbonate content and 2) lithium-only mineralisation that has higher clay content and moderate to high carbonate content. 
• Global Geoscience is focussing its evaluation and testwork on the lithium-boron mineralisation as it potentially is of higher value with lower processing and capital costs.  
• Based on test work completed for Global Geoscience by Kappes Cassiday of Nevada, USA, Hazen Research of Colorado, USA and SGS Minerals of Ontario, Canada and reported by Global Geoscience both the lithium-boron and lithium-only mineralisation have a reasonable expectation of economic extraction. 
• Metallurgical test work has been conducted on drill core and outcrop samples and shows that the lithium-boron mineralisation is amenable to acid leaching (sulphuric).     

Contacts at Global Geoscience

About Global Geoscience

Global Geoscience Limited (ASX:GSC) is an Australian-based lithium-boron mine developer focused on its 100%-owned Rhyolite Ridge Lithium-Boron Project in Nevada, USA.

Rhyolite Ridge is a large, shallow lithium-boron deposit located close to existing infrastructure. It is a unique sedimentary deposit that has many advantages over the brine and pegmatite deposits that currently provide the world’s lithium. Rhyolite Ridge is one of only two known large lithium-boron deposits globally.   

Global Geoscience is aiming to capitalise on the growing global demand for lithium and boron. Lithium has a wide variety of applications that include glass, ceramics, lubricants and its main growth market, batteries. Boron is used in glass, fiberglass, insulation, ceramics, semiconductors, agriculture and many other applications. Global Geoscience aims to develop the Rhyolite Ridge Lithium-Boron Project into a strategic, long-life, low-cost supplier of lithium and boron products. To learn more please visit: www.globalgeo.com.au.

Competent Persons Statement

The information in this report that relates to Mineral Resources is based on information compiled by Mr Robert Dennis who is a Member of the Australasian Institute of Geoscientists and the Australian Institute of Mining and Metallurgy. Mr Dennis is a full time employee of RPM.  Mr Dennis is the Competent Person for this Mineral Resource estimate and has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he has undertaken to qualify as a Competent Person as defined in the 2012 Edition of the ‘Australasian Code for the Reporting of Exploration Results, Mineral Resources and Ore Reserves’. Mr Dennis consents to the inclusion in this report of the matters based on his information in the form and context in which it appears.