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: +44 (0)20 7830 9650
Strand Hanson Limited
Richard Tulloch / James Bellman Tel: +44 (0)20 7409 3494
SI Capital Limited
Nick Emerson Tel: +44 (0)1483 413 500
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").
- END -
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
END
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