Orezone Gold Corporation: Positive Metallurgical and Drill Results from the Bondi Project
OTTAWA, ONTARIO -- (Marketwired) -- 06/04/13 -- Orezone Gold Corporation (TSX: ORE) is pleased to provide an update on a recently completed metallurgical study and the latest drill results for its wholly owned Bondi Gold Project in Burkina Faso, West Africa. Bondi is the Company's second tier project with an NI 43-101 qualified resource of 282,000 oz of Measured and Indicated resources (4.2 Mt @ 2.1 g/t) and 149,700 oz of Inferred resources (2.5 Mt @ 1.8 g/t).
Metallurgical Highlights
-- Direct agitated cyanidation recoveries averaged 94% for oxide, 93% for
semi-oxidized and 91% for sulphide material.
-- Recoveries were greater than or equal to 90% for all of the composite
samples at all grind sizes between 75 micrometre to 106 micrometre,
irrespective of the cyanide concentration used (0.5 to 2.0 gNaCN/L).
-- Rapid gold recovery at all feed sizes; 6 to 12 hours for oxide and
within 12 hours for sulphide.
-- Sulphide samples responded well to the scoping flotation testing at a
grind size of 75 um with 88.3% of the gold recovered in 4.3% of the feed
weight for a composite sample with a grade of 2.2 g/t, and 91.6% of the
gold recovered in 6.8% of the feed weight for a composite sample with a
grade of 6.9 g/t.
Drilling Highlights
-- New infill core holes within the inferred resources were broadly in line
with the resource model and will assist to upgrade those resources to
the indicated category.
-- New RC holes tested auger drill anomalies generated in 2012, extending
zone 372 by about 275 m to the SE, and intersected gold mineralization
about 1,500 m to the south of zone 2S, in the same host rock (porphyry).
Many of the better auger anomalies remain untested.
-- A Mobile Metal Ions (MMI™) geochemical survey test was completed over
a 400 m section where two blind deposits are present (Zone 2NW and 2NE):
the test was conclusive, with a strong gold anomaly over the blind
deposits where conventional soil chemistry did not work. This will be
useful for future target generation and prioritization where the
geophysics indicates strong structures and the conventional soil
geochemistry has been weak.
Metallurgical Study
A suite of thirty-six samples representative of Bondi oxide, sulphide and mixed gold-bearing material were submitted to McClelland Laboratories in Sparks, Nevada last year for detailed head analysis to characterize the samples by grade, cyanide solubility, elemental make-up and carbon and sulphide content. Direct agitated cyanidation tests were performed on all samples at a feed size of 80% passing 75 micrometre and a cyanide concentration of 1.0 g NaCN/L for a standard leach time of 72 hours. The majority of the samples were then combined into four different composites that represented medium grade oxide (MGO), high grade oxide (HGO), medium grade sulphide (MGS) and high grade sulphide (HGS) material. Metallurgical testing of the four composite samples included:
-- direct agitated cyanidation at various feed sizes to determine gold and
silver recoveries, recovery rate, reagent consumption and feed size
sensitivity;
-- direct agitation at various cyanide concentrations to determine optimum
cyanide dosing;
-- mechanically agitated cyanidation to evaluate the benefits of sparging
and the addition of lead nitrate; and
-- Carbon-in-leach (CIL) mechanically agitated cyanidation to determine the
effects of adding activated carbon during leaching.
In addition, metallurgical testing of the two sulphide composite samples included scoping level bulk sulphide flotation at a feed size of 80% passing 75 micrometre, followed by further testing at other feed sizes between 80% passing 106 micrometre and 80% passing 53 micrometre.
Two master composite samples were prepared for gravity testing, combining the MGO and HGO variability samples into an Oxide Master Composite (Oxide MC) and the MGS and HGS variability samples into a Sulphide Master Composite (Sulphide MC), which were both subjected to:
-- scoping level gravity concentration to evaluate recovery using a Knelson
concentrator;
-- extended gravity recoverable gold (E-GRG) to determine the GRG content
of the composite and the distribution of the GRG by particle size; and
-- agitated cyanidation on gravity concentration products to determine
response to cyanidation and optimum leaching conditions for both gravity
concentrate and gravity tails;
A petrographic study of the four composite samples was completed by Economic Geology Consultants from Reno, NV, USA.
Orezone submitted a suite of nineteen whole PQ core samples representative of Bondi oxide, sulphide and mixed gold-bearing material to McClelland Laboratories in June 2012. McClelland submitted in July 2012 four composite whole PQ core samples of oxide (2) and sulphide (2) gold-bearing material to Hazen Research Inc. from Golden, CO, USA, for comminution test work that yielded the following results:
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Comminution Test Oxide Oxide Fresh Fresh
(I1) (S3) (I1) (S3)
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Bond ball mill work index kWh/t 5.9 4.0 21.0 18.1
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Bond crusher work index kWh/t 1.8 1.9 14.3 8.7
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Bond abrasion index Gram 0.001 0.009 0.145 0.053
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Unconfined Compressive Strength Psi
(UCS) 15,960 11,530
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Overall AG-SAG hardness (A x b) 473 584 36 68
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Drop Weight Index kWh/m3 0.6 0.5 8.1 4.1
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Conclusions of the McClelland Laboratories Metallurgical report were:
-- Overall metallurgical performance of the oxide and sulphide gold-bearing
materials was very similar;
-- All variability samples were amenable to whole ore milling cyanidation
treatment at a feed size of 80% passing 75 micrometre and a cyanide
concentration of 1.0 g NaCN/L;
-- Maximum or near maximum gold recoveries for the oxide composites were
obtained at a feed size of 80% passing 75 micrometre;
-- Maximum or near maximum gold recoveries for the sulphide composites were
obtained at a feed size of 80% passing 53 micrometre;
-- Maximum or near maximum gold recoveries for the oxide composites were
obtained at a cyanide concentration of 0.5 gNaCN/L (the lowest
concentration used for this optimization work, leaving possibly room for
improvement);
-- Maximum or near maximum gold recoveries for the sulphide composites were
obtained at a cyanide concentration of 0.5 to 1.0 gNaCN/L;
-- Rapid gold recovery rates were achieved with leaching substantially
complete within twelve hours for most variability samples and composites
evaluated;
-- Air sparging, oxygen sparging and lead nitrate addition during
cyanidation testing did not improve gold recoveries;
-- Sulphide composites responded well to flotation treatment for recovery
of gold;
-- Gravity recoverable gold is generally liberated evenly through the grind
sizes tested;
-- Gold recovery from the cyanidation of gravity products is essentially
the same as that from the whole ore cyanidation.
Recommendations of the McClelland Metallurgical report are:
-- Further optimization of flotation conditions for the sulphide composites
is warranted as they showed high gold recoveries by flotation;
-- Further optimization of the cyanide concentration as gold recoveries did
not decrease for many oxide and sulphide samples at the lowest cyanide
concentration tested (0.5 gNaCN/L), and cyanide concentrations as low as
0.25 gNaCN/L were effective for gravity product cyanidation.
The complete metallurgical report is filed on the Company's website at www.orezone.com.
Exploration and definition drilling
The recent drilling included a 14-hole (2,497 m) core program that targeted Inferred blocks within the existing resource, and a 93-hole (4,581 m) RC program that tested auger drill anomalies generated in 2012 in the area located to the SE of the current resource.
The core drilling program returned results that were broadly in line with the resource model and that will assist to upgrade part of the current Inferred blocks to the Indicated category.
The RC drill program intersected narrow gold mineralization along strike from zone 372 resulting in a possible extension of 275 m to the SE for a total strike length of at least 1,150 m. This zone is still open-ended to the SE, and hole BRC0833 intersected mineralization about 90 m into the footwall of zone 372 where most of the best auger anomalies were not tested due to difficult drilling conditions, including a shallow water table. Hole BRC0833 was stopped in mineralization and intersected 4 m at a grade of 12.6 g/t, including one meter at 43.3 g/t.
Breakdown of Drilling Meterage for this Release
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Zone Core Drilling RC Drilling
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# of holes Total m # of holes Total m
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Z2 11 2,066 0 0
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Z2S 3 431 0 0
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Z2SE 0 0 1 50
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372 0 0 4 179
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GBF 0 0 88 4353
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TOTAL 14 2,497 93 4,581
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Highlights of Core Drilling Results for this Release
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Uncut Cut
From To Length Grade Grade
Zone Section Hole (m) (m) (m) (g/t) (g/t)
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Z2 3550N BDD0058 101.0 103.0 2.0 6.33 5.00
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Z2 3375N BDD0063 156.0 165.0 9.0 6.62 3.55
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Z2 3225N BDD0065 134.0 136.0 2.0 34.91 5.00
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Z2 3225N BDD0065 191.0 201.0 10.0 2.17 1.78
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Z2 3025N BDD0066 169.0 175.0 6.0 2.32 2.18
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Z2 2975N BDD0067 195.0 202.0 7.0 1.89 1.89
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Z2 2900N BDD0068 134.5 142.0 7.5 1.58 1.58
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Z22S 2400N BDD0070 135.0 151.0 16.0 2.54 2.25
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Reverse Circulation ( "RC" ) Drilling Results for this Release
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Uncut Cut
From To Length Grade Grade
Zone Section Hole (m) (m) (m) (g/t) (g/t)
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372 6000 BRC0830 18.00 23.00 5.00 0.63 0.63
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372 6050 BRC0831 21.00 24.00 3.00 1.14 1.14
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372 6100 BRC0832 18.00 23.00 5.00 1.20 1.20
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372 6000 BRC0833 40.00 44.00 4.00 12.60 3.04
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GBF W 5800 BRC0856 12.00 14.00 2.00 0.68 0.68
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GBF W 5400 BRC0868 41.00 45.00 4.00 0.72 0.72
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GBF W 5400 BRC0874 35.00 47.00 12.00 0.96 0.96
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GBF W 5400 BRC0874 52.00 55.00 3.00 0.94 0.94
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GBF W 5400 BRC0875 22.00 24.00 2.00 0.88 0.88
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GBF W 5200 BRC0892 15.00 19.00 4.00 2.21 2.21
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GBF W 5200 BRC0892 33.00 35.00 2.00 1.01 1.01
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The mineralized intervals are based on a lower cut-off grade of 0.5 g/t, a minimal width of 2 m and up to a maximum of one meter of dilution being included. Grades are weighted average of individual assays. Cut grades use a top-cut of 5 g/t as per historical procedures. The true width of the mineralization is approximately 70% of the drill length interval. The half-core samples were collected by Orezone employees using a diamond saw. The core samples were prepared by SGS Burkina Faso s.a.r.l. at the Bombore site facility and then split by Orezone to 1 kg using Rotary Sample Dividers (RSDs). A 1 kg aliquot was analyzed for leachable gold at BIGS Global Burkina s.a.r.l in Ouagadougou, by bottle-roll cyanidation using a LeachWell™ catalyst.
The RC drilling samples were divided by Orezone employees using Rotary Sample Dividers (RSDs). A 2 kg split was prepared by SGS Burkina Faso s.a.r.l. at the Bombore site facility and then split by Orezone to 1 kg using Rotary Sample Dividers (RSDs). A 1 kg aliquot was analyzed for leachable gold at BIGS Global Burkina s.a.r.l in Ouagadougou, by bottle-roll cyanidation using a LeachWell™ catalyst. The leach residues from all samples with a leach grade in excess of 0.2 g/t were prepared by BIGS Global Burkina s.a.r.l. and then split by Orezone to 50 g using Rotary Sample Dividers (RSDs). A 50 g aliquot was analyzed by fire assay at SGS Burkina Faso s.a.r.l.. Orezone employs a rigorous Quality Control Program (QCP) including a minimum of 10% standards, blanks and duplicates.
Qualified Persons
The drilling program was executed under the supervision of Pascal Marquis, SVP Exploration for Orezone; the report titled "Report on Metallurgical Testing - Bondi Drill Samples, MLI Job No. 3685" was prepared under the supervision of J. McPartland, Metallurgist and VP Operations at McClelland Laboratories. All are Qualified Persons under National Instrument 43-101 and approved their respective technical information in this release.
About Orezone Gold Corporation
Orezone is a Canadian company with a gold discovery track record of +12 Moz and recent mine development experience in Burkina Faso, West Africa. The company owns a 100% interest in Bombore which is situated 85 km east of the capital city, adjacent to an international highway. Mineral resources are constrained within optimized open pit shells that span 11 km, and include 4.13 Moz of measured and indicated (125 Mt @ 1.03 g/t) and 1.03 Moz of inferred resources (35 Mt @ 1.00 g/t) with an average depth of drilling to only 120 meters. The Company is completing a Feasibility Study ("FS") at Bombore for a phase one oxide-only CIL plant in 2H 2013 in order to become a mid-tier gold producer.
FORWARD-LOOKING STATEMENTS AND FORWARD-LOOKING INFORMATION: This news release contains certain "forward-looking statements" within the meaning of applicable Canadian securities laws. Forward-looking statements and forward-looking information are frequently characterized by words such as "plan", "expect", "project", "intend", "believe", "anticipate", "estimate", "potential", "possible" and other similar words, or statements that certain events or conditions "may", "will", "could", or "should" occur. Forward-looking statements in this release include statements regarding, among others; upgrading Bondi resources, improved metallurgical recoveries, completing a FS in 2H 2013, and becoming a mid-tier gold producer.
FORWARD-LOOKING STATEMENTS are based on certain assumptions, the opinions and estimates of management at the date the statements are made, and are subject to a variety of risks and uncertainties and other factors that could cause actual events or results to differ materially from those projected in the forward-looking statements. These factors include the inherent risks involved in the exploration and development of mineral properties, the uncertainties involved in interpreting drilling results and other geological and geotechnical data, fluctuating metal prices, the possibility of project cost overruns or unanticipated costs and expenses, the ability of contracted parties (including laboratories and drill companies to provide services as contracted); uncertainties relating to the availability and costs of financing needed in the future and other factors. The Company undertakes no obligation to update forward-looking statements if circumstances or management's estimates or opinions should change. The reader is cautioned not to place undue reliance on forward-looking statements. Comparisons between any resource model or estimates with the subsequent drill results are preliminary in nature and should not be relied upon as potential qualified changes to any future resource updates or estimates.
Readers are advised that National Instrument 43-101 of the Canadian Securities Administrators requires that each category of mineral reserves and mineral resources be reported separately. Readers should refer to the annual information form of Orezone for the year ended December 31, 2012 and other continuous disclosure documents filed by Orezone since January 1, 2013 available at www.sedar.com, for this detailed information, which is subject to the qualifications and notes set forth therein.
Contacts:
Orezone Gold Corporation
Ron Little, CEO
(613) 241-3699
Toll Free: (888) 673-0663
rlittle@orezone.com
Orezone Gold Corporation
Pascal Marquis, SVP Exploration
(613) 241-3699
Toll Free: (888) 673-0663
pmarquis@orezone.com