TIDMGGG
RNS Number : 9697R
GGG Resources PLC
14 November 2011
GGG Resources plc
(the "Company" or "GGG")
Bullabulling Gold Project - Initial Metallurgical Programme
Results
Highlights:
-- Metallurgical study of primary mineralisation (between
Bacchus and Phoenix pits on the ullabulling Trend) completed.
-- Key inputs to a large scale carbon-in-leach operation now determined.
-- Gold recoveries expected to exceed 90% for grades above 0.6 g/t Au.
-- Master composite sample grading 0.96 g/t Au obtained 92.5% recovery over 24 hours.
-- Mineralisation soft to medium hardness and moderate abrasiveness.
-- The project is amenable to SAG milling and possibly high pressure grinding rolls (HPGR's).
-- A follow-up metallurgical programme now underway to finesse
optimum grind size, reagents and recoveries.
Jeff Malaihollo, Managing Director of GGG Resources said "The
metallurgical results are highly encouraging and confirm that the
Bullabulling Gold project has excellent recoveries at head grades
of less than 1.0g/t Au with the master composite producing
recoveries of over 90% with low cyanide consumption. Previous
operations during the 1990's produced average recoveries of
approximately 94%. The Bullabulling mineralisation is not hard or
abrasive in the context of the Eastern Goldfields which should have
a positive impact on operating costs. Bullabulling continues to
demonstrate all of the characteristics of a robust long term gold
project."
The Bullabulling Joint Venture is pleased to announce the
results of the first stage comprehensive metallurgical test work on
fresh mineralisation at the Bullabulling Gold Project. The final
report for the Phase One test work has been received, based on five
samples, which were composited to a master composite sample and the
remaining samples were the subject of variability test work. The
samples were selected from fresh (primary) mineralisation taken at
intervals along the Bullabulling Trend between Bacchus pit in the
south and Phoenix pit in the north (see sample location map).
The results from both the test work on the composite sample and
the variability test work are highly encouraging with the results
confirming that the Bullabulling gold deposit has excellent
recoveries at head grades of less than 1.0 g/t Au, with
approximately 40% of the contained gold recoverable by gravity. The
gold recoveries are sensitive to grind size and additional test
work is planned to optimise the required grind.
Compared to other deposits in the Goldfields, the ore at
Bullabulling is neither hard nor abrasive due to the lack of quartz
associated with the gold mineralisation. This should have a
positive impact on operating costs. Planning and sampling of
additional ore from the entire length of the Bullabulling Trend to
increase the number of variability test work samples has commenced
and these data will be used in the next phase of work to more
accurately estimate processing and capital costs and assess
recoveries at lower head grades.
Metallurgy Test Work
A programme of diamond drilling was completed to provide fresh
sample material for extractive and comminution testing. Five PQ
size diamond core holes, two collared at the base of Bacchus South
and Phoenix pits drilling directly into fresh rock, and three from
surface requiring pre-collars to reach the base of oxidation prior
to commencing PQ diamond tails, were completed for a total of 506m
(see sample location map). Holes were designed to intersect gold
mineralised zones in fresh rock as defined by the resource model,
ranging from 10m to 19m in width to obtain sufficient sample (330kg
per hole) for the test work. Where possible, drillholes were
oriented partially down the dip of mineralised zones in order to
extend the intersection width. All mineralised samples contained
visible silicification and disseminated sulphide mineralisation at
the contact with felsic and mafic lithologies. All core was logged
and photographed before selecting 20-25m (300kg) mineralised
intervals from each drillhole for transportation to Perth where
they were assayed and prepared for processing. The core was
reviewed and various samples selected for comminution (crushing and
grinding), recovery and variability test work based on the assay
results to produce one composite sample of approximately 1.0 g/t Au
and five samples for variability test work. The metallurgical test
work programme included the following:
-- Sample preparation.
-- Head assay analysis.
-- Comminution test work.
-- Gravity separation and cyanidation optimisation.
-- Lime demand test work.
-- Carbon loading test work.
-- Oxygen uptake rate determination.
-- Rheology test work.
Process water, obtained from the existing borefield at
Bullabulling, was used for all parts of the test programme where
wet grinding and slurry preparation were required.
The head assay analysis on the master composite sample gave a
grade of 0.96 g/t Au, 0.3 g/t Ag, 150 ppm As and 0.88% S. The
variability samples gave grades ranging 0.56-5.44 g/t Au, 0.3-0.8
ppm Ag, <10-480 ppm As and 0.42-1.32% S (Table 1). It is
considered that the variability samples provided a complete range
of potential ore types from low grade to high grade samples.
Comminution
A comprehensive testwork programme was performed on samples from
the five sample drill holes, with most of the testwork being
performed on composite samples from the mineralised intervals in
each drillhole ('comminution composites'). The comminution
composites were submitted for a range of test work, including:
SAG Amenability Unconfined Compressive Strength
(UCS)
---------------- --------------------------------
Bond Impact Crushing
---------------- --------------------------------
JK Drop-weight
---------------- --------------------------------
Bond Abrasion
---------------- --------------------------------
Bond Rod Mill
---------------- --------------------------------
Bond Ball Mill
---------------- --------------------------------
Variability SAG Mill Comminution (SMC)
---------------- --------------------------------
Bond Ball Mill
---------------- --------------------------------
The UCS values ranged from 5.4 to 161.3 MPa with an average of
101 MPa; the range spans Very Soft to Competent material, and
indicates SAG milling would be an appropriate process option. The
Bond Crushing Work Indices recorded ranged from 4.6 to 18.1 kW/t,
averaging 8.8 kW/t. Apart from the high outlier readings the
samples are considered soft to medium with respect to impact
resistance and are generally lower than average for typical Eastern
goldfields type gold deposits. The Bond Rod Mill Work Indices were
consistently higher than the Ball Mill Work Indices averaging 15.7
and 12.5 kWh/t respectively. The Crushing Work Indices reported
were significantly lower than the Rod and Ball Milling figures,
which also supports the inclusion of a SAG mill in the process
flowsheet. The Bond Abrasion Indices varied from 0.14 to 0.27
averaging 0.19 which is moderately abrasive. The Drop Weight and
SMC testing indicate the samples exhibit significant resistance to
both impact and abrasion breakage and indicate High Pressure
Grinding Rolls (HPGR's) should be considered to realise power
efficiencies.
Gold Extraction
A thorough gravity and leach test programme was undertaken on
the Master Composite with tests under optimum conditions performed
on Variability Samples to evaluate:
-- Suitability of gravity gold recovery
-- Optimum grind size
-- Use of sparged oxygen
-- Use of lead nitrate
-- Initial and maintained cyanide concentrations
As a result of the testwork, the following optimum conditions
were selected:
-- Gravity separation ahead of leaching
-- Gravity grind P80 of 150 microns
-- Leach grind P80 of 75 microns
-- Leach with oxygen sparging
-- Lead nitrate addition of 250g/t
-- Initial cyanide level of 0.1%
The inclusion of gravity separation ahead of leaching achieved
marginally higher gold recoveries over direct leaching, depending
on the duration of leaching. Gravity recoveries typically range
between 30% and 50% of total gold extraction and further work is
required to determine the optimum design. Grinding optimisation was
a major component of the testwork program, as power will be a
significant operating cost and comminution efficiency must be
maximised.
The testwork indicates the optimum grind is a P80 of 75 microns
but further work will be undertaken to define whether a coarser
grind (between 75 and 106 microns) is beneficial. Leach extractions
exceeding 90% are expected for all types of mineralisation
(including low head grades), with cyanide consumption of around 0.8
kg/t and lime at 5 kg/t or higher. The recovery test work results
for the master composite sample (0.96 g/t Au) gave 93.57% recovery
after 48 hours with 45% of the gold reporting to gravity (Table 1).
Lime and cyanide consumption were 6.89 and 0.39 kg/t respectively.
The variability recovery test work gave similar recoveries but
slightly different cyanide and lime consumption. The lower recovery
of 89% for the variability sample with a head grade of 0.56 g/t Au
suggests that recoveries may be sensitive to head grades below 0.6
g/t Au. Additional variability test work is required to test this
possibility. The composite sample was also tested at four different
grind sizes and the results suggest that the ore from Bullabulling
is sensitive to grind size with the 75 micron sample giving the
best recovery of 94.8%, with recoveries reducing to 88.58% at a 150
micron grind (Table 2).
Sample Au g/t Gravity % Au Extraction (Hours Consumption
% ) (kg/t)
--------- ------- -------- ------------------------------ --------------
2 8 24 48 Lime NaCN
--------- ------- -------- ------ ------ ------ ------ ------ ------
Master 0.96 45.00 87.01 91.15 92.51 93.17 6.89 0.39
--------- ------- -------- ------ ------ ------ ------ ------ ------
HS25168 0.56 27.59 86.51 86.51 87.76 88.97 4.72 0.82
--------- ------- -------- ------ ------ ------ ------ ------ ------
HS25169 5.44 47.73 93.86 94.42 96.93 97.61 4.92 0.89
--------- ------- -------- ------ ------ ------ ------ ------ ------
HS25170 2.18 42.79 91.29 94.26 95.40 97.05 5.49 0.88
--------- ------- -------- ------ ------ ------ ------ ------ ------
HS25171 1.60 52.50 90.33 92.57 94.00 94.70 5.33 0.78
--------- ------- -------- ------ ------ ------ ------ ------ ------
HS25172 1.53 47.53 92.10 93.49 93.49 93.49 5.23 0.88
--------- ------- -------- ------ ------ ------ ------ ------ ------
Table 1: Variability recovery test work results from individual
samples
Sample Grind Gravity % Au Extraction (Hours) Consumption
(microns) (kg/t)
--------- ----------- -------- ------------------------------ --------------
2 8 24 48
--------- ----------- -------- ------ ------ ------ ------ ------ ------
HS24786 150 33.97 77.62 85.72 87.65 88.58 6.90 0.68
--------- ----------- -------- ------ ------ ------ ------ ------ ------
HS24787 125 34.71 79.30 87.60 89.57 90.52 6.80 0.67
--------- ----------- -------- ------ ------ ------ ------ ------ ------
HS24788 106 36.28 80.68 89.33 90.36 90.85 6.87 0.77
--------- ----------- -------- ------ ------ ------ ------ ------ ------
HS24789 75 35.22 85.33 91.61 93.11 94.08 6.84 0.97
--------- ----------- -------- ------ ------ ------ ------ ------ ------
Table 2: Grind size recovery test results from the composite
sample
Initial Cyanide % Au Recovery
(%) (24 hrs)
---------------- --------------
0.200 94.84
---------------- --------------
0.100 94.40
---------------- --------------
0.075 92.08
---------------- --------------
0.050 91.85
---------------- --------------
0.025 86.81
---------------- --------------
Table 3: Summary of Cyanidation Testwork
Future Metallurgical Test Work Plan
Although the metallurgical test work for the scoping study is of
a very high quality and gave results similar to previous
operational data, additional variability data are required from the
entire length of the Bullabulling Trend that potentially may be
mined. A programme of PQ diamond drilling to obtain core samples
for the variability testing using the optimised pit shells from the
scoping study has been agreed by the metallurgical consultant and
completed (see sample location map). The metallurgical drilling
programme comprises 17 drillholes totalling 1,935m including 770m
of RC drilling in 15 pre-collars and approximately 1,100m of PQ
size diamond drill core. The drilling provided 27 samples (each
300kg in weight of full PQ core) made up of mineralised
transitional partly oxidised material and fresh material.
The drilling and testwork are critical path tasks for the
pre-feasibility study, consequently this work has commenced and
currently well ahead of schedule. Additional water sampling for the
pre-feasibility study test work has also been completed and the
sample delivered to the laboratory in Perth.
Bullabulling Overview
The Bullabulling Gold project (Bullabulling) is a large tonnage,
low grade deposit with high grade shoots, associated with the
regional Bullabulling shear zone which extends over tens of
kilometres. The mineralised structure is 500m wide, consisting of
multiple west dipping low grade stacked zones with narrower higher
grade gold mineralisation. Bullabulling is located near Coolgardie
and approximately 65km south-west of Kalgoorlie, Western Australia.
Previous operations produced 371k oz Au in the 1990's. The current
programme focuses on the 6km portion of the shear zone known as the
Bullabulling Trend where previous operations were concentrated. The
focus for the Bullabulling joint venture between Auzex Resources
Ltd and GGG Resources plc is to establish an initial reserve
exceeding one million ounces gold to commence production in
2015.
On 15 August 2011 the Joint Venture announced an updated JORC
compliant resource estimate based on the Phase One drilling
programme of approximately 35,000m. The new JORC compliant resource
is 78.84 Million tonnes at 1.03 g/t gold for 2,603,000 ounces,
using a 0.5 g/t gold cut-off. Of the 2.6 Million ounces of
resource, 711,700 ounces are in the indicated category.
Glossary:
Comminution is the process in which solid materials are reduced
in size, by crushing, grinding and other processes.
Sparging is a technique which involves bubbling a chemically
inert gas through a liquid.
The sample location map referred to in this announcement is
available on the version of this release available on the Company's
website www.gggresources.com.
Further information, please contact:
Dr. Jeffrey Malaihollo David McArthur
MD, GGG Resources plc (UK) GGG Resources plc (Australia)
Tel: + 44 1992 531820 BBG Management Pty Ltd
www.gggresources.com 41 Stirling Highway
Nedlands, WA 6009, Australia
Tel: + 61 8 9423 3200
------------------------------ --------------------------------
Westhouse Securities Limited Collins Stewart Europe Limited
(UK Nominated Adviser) (Broker)
Tom Price / Martin Davison John Prior / Adam Miller
Tel: + 44 20 7601 6100 Tel: + 44 20 7523 8350
------------------------------ --------------------------------
Neil Boom David Brook
MD, Gresham PR Ltd (UK). Professional Public Relations
Tel: + 44 7866 805 108 (Australia media)
T: + 61 8 9388 0944/ +61 433
112 936
E: david.brook @ppr.com.au
------------------------------ --------------------------------
This information is provided by RNS
The company news service from the London Stock Exchange
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