Goldstone Resources Ltd Preliminary in-country metallurgical test work (8930Y)

TIDMGRL

RNS Number : 8930Y

Goldstone Resources Ltd

11 December 2017

11 December 2017

GOLDSTONE RESOURCES LIMITED

("GoldStone" or the "Company")

PRELIMINARY IN-COUNTRY METALLURGICAL TEST WORK

GoldStone Resources Limited (AIM: GRL) is pleased to announce the results of preliminary metallurgical test work on the AK01 proposed North and South pits on the Akrokerri licence, which have returned encouraging results and indicate the potential for heap leach processing of the oxide mineralisation. The Company is conducting preliminary metallurgical test work on samples obtained from the recent trenching to establish a range of potential processes for the development of the project.

Highlights

-- Column tests show the AK01 oxide zone is extremely amenable to both the heap leach and to the CIL gold recovery processes

   --        Gravity recovered gold of 14.8% and 25.4% in the North and South Pit samples respectively 

-- Gold extraction from the tailings produced by the gravity tests were 90.2% and 93.5% for the North and South pit samples respectively using bottle roll test work with carbon(1)

-- Column leach testing indicates moderate cement requirements, with 8 kg/tonne ("kg/t") addition rate enhancing the leaching efficiency and yielding acceptable column slump levels(2)

-- Column leach testing over a 30 day period resulted in recoveries of some 82.6% and 84.7% for the North and South pit samples respectively with cement addition of 8 kg/t

Notes:

1. Samples pulverised to all passing 75 microns prior to leaching by sodium-cyanide solution both with and without carbon in bottle roll tests over 24 hour periods.

2. 4.5% & 3.3% column height slump in the North and South pit sample columns respectively utilising 8 kg/t binder material addition.

Preliminary Metallurgical Test Work on the AK01 North and South Pits for Oxide Heap Leaching

Preliminary metallurgical test work to assess the amenability of the oxide mineralisation to processing by heap leaching has been completed at the University of Mines and Technology (UMaT) in Tarkwa, Ghana under the supervision of Prof. Amankwah, the Dean of the Faculty of Mineral Resource Technology and Ghana's leading expert in the metallurgy of the Ashanti shear system.

The test work was undertaken to ascertain the elemental and mineralogical composition of the ore as well as its gravity recoverable gold and cyanide amenability. The test work included: head assays; sulphur and carbon speciation data; mineralogical composition, for 32 elements; gravity recoverable gold, to determine coarse gold presence; best leaching method using bottle rolls with and without carbon; and column leach testing.

The test work is regarded as preliminary as the samples were from the deep trenches, completed in September 2017, within the oxide zone of the AK01 North and South proposed pits, taken approximately 5 to 6 metres in depth below surface.

The head assays of the composite samples from the AK01 North and South pits averaged 1.74 g/t Au and 1.71 g/t Au respectively, utilising conventional fire assay.

Column Leach Test Work

The samples, 23 kg each, were agglomerated without any size reduction, using cement as a binder at addition rates of 6 kg/t and 8 kg/t prior to column leach testing with a diluted sodium-cyanide (NaCN) solution of 200 ppm, for a duration of 28 days and two additional days washing. The column leach test is an industry-standard method used to provide an indication of leaching performance in a scaled-up heap leach in the field.

Figure 1: http://www.rns-pdf.londonstockexchange.com/rns/8930Y_-2017-12-10.pdf

The test work indicated that the addition of cement at 8 kg/t yielded very good returns, with gold dissolution results amounting to some 82.6% and 84.7% for the North and South pits respectively, which is very encouraging, particularly when coupled with the rapid leach kinetics which saw an extraction level of greater than 70% achieved within 15 days, see Figure 2.

The slump levels achieved during the column leach test work ranged between 4.5% and 3.3% drop in column height from the North and South pit columns respectively, utilizing 8 kg/t cement addition. This would indicate that we have a competent ore that percolates well.

Figure 2: http://www.rns-pdf.londonstockexchange.com/rns/8930Y_1-2017-12-10.pdf

It is worth noting that following the completion of the column leach test work the calculated head grades were higher than the conventional assayed head grades of the respective pit samples. This might be due to the presence of coarse gold particles in the ore. The calculated head grades of the North and South pits averaged 2.73 g/t Au and 2.86 g/t Au respectively.

To confirm the presence of coarse gold and verify the calculated head grades, sub-samples were taken through screen fire assay. The results showed that the grades by screen fire assay were higher than the conventional fire assays and had a good correlation with the calculated head assays. Screen fire assaying results were 2.58 g/t Au and 2.78 g/t Au for the North and South pits respectively.

Whilst the potential presence of coarse gold particles is encouraging news, the Company is undertaking further checks by screen fire assaying composite samples taken from the recent RC drill chips at various depths within the oxide zone of the mineralised deposit. The results for which will be reported when available.

Goldstone's CEO, Emma Priestley commented:

"This preliminary test work on samples from the proposed pits is encouraging, showing that almost 90% of the recoverable gold via the heap leach method is achieved within the first 15 days of leaching. This indicates that a scale up to mine operation would be very successful. Whilst we are currently maintaining a bias towards oxide material, we are also maintaining focus to exploit the development of the higher grade sulphide zone."

Information in this announcement has been reviewed by Malcolm Crowe, an independent consultant with 45 years' experience in mining, minerals and mineral processing, of which some 15 years were spent at the Obuasi Gold Mine, now owned by AngloGold Ashanti. Malcolm is a Fellow of the Institute of Materials Minerals and Mining and a Chartered Engineer and accordingly, is a qualified person as required under the AIM Rules.

For further information, please contact:

 
 GoldStone Resources Limited 
 Bill Trew / Emma Priestley        Tel: [phone] 
 
 Strand Hanson Limited 
 Richard Tulloch / James Bellman   Tel: [phone] 
 
 SI Capital Limited 
 Nick Emerson                      Tel: [phone] 
 

The information contained within this announcement is deemed by the Company to constitute inside information as stipulated under the Market Abuse Regulations (EU) No. 596/2014 ("MAR").

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About GoldStone Resources Limited

GoldStone Resources Limited (AIM: GRL) is an AIM quoted exploration company with projects in Ghana, Senegal, and Gabon that range from grassroots to advanced exploration.

The Company is focused on developing the Homase-Akrokerri project in south-western Ghana, which hosts an existing 602,000 oz gold JORC Code compliant resource at an average grade of 1.77g/t, along strike from the Obuasi Gold Mine, one of the World's major gold mines with a total historical and current resource in excess of 70 million ounces of gold. It is the Company's intention to build a portfolio of high-quality gold projects in Ghana, with a particular focus on the highly prospective Ashanti Gold Belt.

This information is provided by RNS

The company news service from the London Stock Exchange

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December 11, 2017 02:00 ET (07:00 GMT)