- Test work completed by ALS Metallurgy ("ALS") from Kamloops, BC
- Gold recovery up to 96% for the South Cluster composites samples using a combination of flotation and cyanidation
- Results to be incorporated into the Preliminary Economic Assessment ("PEA")
- Phase 3 Testing will conduct separate testing on individuals samples from all zones
VANCOUVER, BRITISH COLUMBIA--(Marketwired - July 25, 2013) - Integra Gold Corp. (TSX VENTURE:ICG) ("Integra" or the "Company") is pleased to announce it has completed Phase 2 metallurgical testing at its Lamaque Gold Project in Val d'Or, Québec. The Phase 2 metallurgical program was designed to examine further flow sheet schemes and assess the metallurgical response of samples of various grades from the South Cluster area (No. 4 Plug and Triangle Zone) with the objective of improving gold recovery from Phase 1 testing. Phase 1 testing (results announced May 1, 2013) was limited to gravity and cyanidation testing and resulted in up to 98% recoveries for the North Cluster composites (Forestel and Parallel Zones) and up to 92% for the South Cluster samples (No. 4 Plug and Triangle Zone). The new flow sheet included the addition of flotation followed by cyanide leach extraction of the generated test products.
"Results of Phase 2 metallurgical work has exceeded our expectations with a substantial increase in gold recovery achieved on South Cluster samples. Phase 2 testing clearly indicates that gold recovery can be optimized to over 95% which is consistent with what was historically achieved on similar types of mineralization at the neighbouring Lamaque and Sigma mines," commented Company President and CEO, Stephen de Jong. "Following these positive results we will be initiating a third phase of metallurgical testing that will focus on optimizing gold recovery using a combination of flotation, cyanidation, and gravity concentration on separate zones/deposits instead of on composites samples, while further optimizing on grind, leach time, and cyanide consumption. We anticipate having this work completed towards the end of the year."
The following table gave a summary of optimized recoveries obtained for Phase 2 work and compared it to Phase 1 results:
|Phase 2 versus Phase 1 Gold Recoveries
||Phase 1 Results
Gravity Separation + Cyanidation
(% Au recovery)
|Phase 2 Results
Flotation + Cyanidation
(% Au recovery)
(equal weight mix of individual samples, grading approximately 9 g/t)
|Cutoff Grade Composite
(sample grading approximately 3 g/t Au)
(sample grading approximately 6 g/t Au)
(sample grading approximately 15 g/t Au)
Summary of Phase 2 Metallurgical Testing
The metallurgical test work for this program focused on a Master Composite comprised of equal parts of the three different sample grade composites from the South Cluster, followed by testing on the component composites. The testing consisted of a rougher sulfide flotation using Potassium Amyl Xanthate (PAX) as the collector, and Methyl Isobutyl Carbonyl (MIBC) as a frother at natural pH. The flotation of the sulfide minerals was followed by a finely ground intensive cyanidation leach extraction test of the flotation rougher concentrate and a less intensive cyanidation leach of the rougher tailing.
Master Composite Performance
Three sets of tests were conducted on the South Cluster Master Composite. Between 84% and 88% of the gold was recovered in sulfide floats to rougher concentrates. The rougher concentrates were reground to about 7 microns K80 and leached using a 5,000 ppm NaCN solution at pH 11.0. The rougher tailings were then leached in a 1,000 ppm NaCN solution at pH 11.0 to extract gold not recovered via flotation giving overall gold recovery between 93.6% and 96%.
Finer primary grinding increased gold recovery to the rougher concentrate as well as leach recovery from the final tails. Decreasing the primary grind size from 206 to 107 microns K80 increased overall gold recovery by about 2%. Approximately 12% to 16% of the gold in the rougher feed remained in the rougher tailings. Leaching of the rougher tailings recovered 67% and 72% of the remaining gold at primary grind sizing of 206 and 107 microns K80, an economic assessment is recommended to determine whether leaching of the rougher tails and which primary grind size would be most beneficial.
Individual Composite Performance
The flowsheet used for the South Cluster Master Composite was applied in duplicate to the three component composites. A grind size targeting 200 microns K80 was chosen. The rougher concentrates were reground between 8 to 10 microns K80 and leached using a 5,000 ppm NaCN solution at pH 11.0. The rougher tailings were leached in a 1,000 ppm NaCN solution at pH 11.0 to recover gold not recovered by flotation.
Gold recovery to the rougher concentrates varied across the composites averaging 75%, 88% and 84% from the Cutoff, Average and High Grade composites respectively; 98% to 99% of this was extracted to cyanide leach liquors. Leaching of the rougher tailings increased overall gold recoveries to the leach liquors to about 90% in the Cutoff Grade composite and 95% in the Average and High Grade composites. Overall gold recoveries between the duplicate tests varied less than 1%. In Phase 1 testing, overall recoveries using a gravity concentration followed by leaching of the gravity tails resulted in recoveries of maximum 92% which were achieved when primary grinds were about 50 microns K80 and leach durations were 96 hours.
Cyanide consumptions in the leaches under the flotation/cyanidation flowsheet and conditions were about 3 kg/tonne feed; a direct comparison of cyanide consumption to the gravity plus cyanidation flow sheet from Phase 1 cannot be made as the gravity concentrate was never subjected to a cyanide leach. An economic assessment of the energy and capital costs would have to be completed to determine which grind size and flowsheet configuration has the most economically cost effective extraction method. Further optimization of the cyanide leach process may result in lower cyanide consumptions and should be considered for future test programs.
Phase 3 Metallurgical Testing
A third phase of metallurgical testing will focus on optimizing gold recovery using a combination of flotation, cyanidation, and gravity concentration but on separate samples from each individual zone instead of on Cluster composites, namely on the Triangle, Plug No. 4, Parallel, and Forestel zones. Further optimization of sample grind sizing, leach time, and cyanide consumption are also to be performed. The results will provide comprehensive flowsheet information for processing material at Lamaque. We anticipate initiating Phase 3 in the fall with work to be completed towards the end of 2014.
Project and Company Profile
Integra's Lamaque Gold Project is located in the heart of the Val d'Or gold camp in the Province of Québec, Canada, approximately 550 km northwest of Montréal. Québec is rated one of the best mining jurisdictions in the world. Infrastructure, human resources and mining expertise are readily available.
The Company's primary objective is to continue to prove up additional resources while advancing the existing resource towards production. The project is split into two clusters, the North and South Clusters, which are located approximate 1 kilometer ("km") from each other. The Lamaque Project's primary target, the South Cluster which presently consists of the Plug No. 4 and Triangle zones, is 3 km from the City of Val d'Or. The North Cluster, presently consisting of the Parallel and Fortune zones, is located 1 km from the city.
The Lamaque exploration project is under the direct supervision of Hervé Thiboutot, P.Eng. and Senior Vice-President of the company, Francois Chabot, Eng. and Manager Operations of the Company, both Qualified Person ("QP") as defined by National Instrument 43-101; Alain-Jean Beauregard, P.Geo., and Daniel Gaudreault, Eng., Geo. of Geologica Inc., both independent QP as defined by National Instrument 43-101. The Company's QPs have reviewed the technical content of this release.
Quality Assurance - Quality Control ("QA/QC")
Thorough QA/QC protocols are followed on the project including insertion of duplicate, blank and standard samples in all drill holes. The core samples are submitted directly to ALS Laboratory Group and Bourlamaque Labs in Val-d'Or for preparation and analysis. Analysis is conducted on 1 assay-ton aliquots. Analysis of Au is performed using fire assay method with atomic absorption finish, with a gravimetric finish completed for samples exceeding 5 g/t Au, or a metallic sieve assay for samples containing visible gold. When available the gravimetric or metallic sieve assay results are used for the reported composite intervals. Metallurgical work described in this press release was completed by ISO 9001 compliant ALS from Kamloops, BC.
ON BEHALF OF THE BOARD OF DIRECTORS
Stephen de Jong, CEO & President
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Cautionary Note Regarding Forward Looking Statements: Certain disclosure in this release constitute forward-looking statements. In making the forward-looking statements in this release, the Company has applied certain factors and assumptions that are based on the Company's current beliefs as well as assumptions made by and information currently available to the Company, including that the Company is able to obtain any government or other regulatory approvals required to complete the private placement and Company's planned exploration activities, that the Company is able to complete the private placement, that the Company is able to procure personnel, equipment and supplies required for its exploration activities in sufficient quantities and on a timely basis and that actual results of exploration activities are consistent with management's expectations. Although the Company considers these assumptions to be reasonable based on information currently available to it, they may prove to be incorrect, and the forward-looking statements in this release are subject to numerous risks, uncertainties and other factors that may cause future results to differ materially from those expressed or implied in such forward-looking statements. Such risk factors include, among others, that the private placement will not be completed, that actual results of the Company's exploration activities will be different than those expected by management and that the Company will be unable to obtain or will experience delays in obtaining any required government approvals or be unable to procure required equipment and supplies in sufficient quantities and on a timely basis. Readers are cautioned not to place undue reliance on forward-looking statements. The Company does not intend, and expressly disclaims any intention or obligation to, update or revise any forward-looking statements whether as a result of new information, future events or otherwise, except as required by law.