International Tower Hill's Livengood Project ReturInternational Tower Hill's Livengood Project Returns 89% Gold Recovery From Recent Metallurgical Testwork
Potential to dramatically enhance project economics
- Wednesday April 15, 2009, 9:00 am EDT
https://finance.yahoo.com/news/International-Tower-Hills-iw-14930842.html
VANCOUVER, BRITISH COLUMBIA--(MARKET WIRE)--Apr 15, 2009 -- International Tower Hill Mines Ltd. ("ITH" or the "Company") (CDNX:ITH.V - News)(AMEX:THM - News)(Frankfurt:IW9.F - News) is pleased to announce positive results from its ongoing metallurgical studies on the Livengood deposit, Alaska. The most recent results, performed by Kappes Cassiday & Associates of Reno, Nevada, focused on testing gold recovery enhancement. The tests followed a proven gold recovery flow-sheet which utilized a combination of grinding, gravity concentration and cyanide leaching of the tails to increase average recoveries by 15% in the oxide/transition rock and by 30% in the un-oxidized rock, resulting in a global average gold recovery of 89%. The significant increase in gold recovery indicates the economics of the Livengood deposit could be greatly enhanced by a high recovery milling operation for the higher grade ore and a low grade heap leach operation for the lower grade material, similar to that employed by the producing Fort Knox Mine located 60 miles to the south. Additional testwork will seek to further improve and refine these encouraging results.
A summary of the gold recovery profiles for the two major ore types is shown in Table 1 with individual samples detailed in Table 2.
Table 1
Summary of Livengood Metallurgical Results
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% Gold Recovery
Mineralization % Gold Recovery % Gold Recovery (-200 mesh +
Type (-10 mesh) (-200 mesh) Gravity Con)
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Oxide-Transitional 76% 82% 91%
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Un-Oxidized 57% 71% 87%
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Jeff Pontius, President and CEO of the Company, stated, "The extremely positive metallurgical testwork results confirms earlier indications on recovery optimization through grinding and will open the door to a much more economically robust project at Livengood. This information, linked with the ongoing success the Company is enjoying in developing large, higher grade (+1 g/t gold) zones as well as the tremendous depth potential of these zones, paints an exceptional picture for a potential expansion of the existing gold resource and a corresponding increasing economic potential."
Metallurgical Testing Results
The recent recovery tests were conducted on twenty four representative samples that had undergone previous minus 10 mesh (-10 mesh) bottle roll tests to determine if recoveries could be enhanced through grinding (milling option). Compared to the -10 mesh leaching tests, the new data indicate that minus 200 mesh (-200 mesh) grinding plus gravity concentration increases average recoveries by 15% in the oxide/transition rock and by 30% in the un-oxidized rock. The average concentration ratio of the gravity concentrates is exceptional, averaging approximately 100 to 1, resulting in a high-grade concentrate that averages 87.87 g/t gold. Cyanide recovery on the tails after concentrate extraction is still 60%, resulting in high overall gold recovery for all ore types. Further testing will determine if the gravity concentrate requires additional grinding in order to maximize gold extraction.
Table 2: Cyanide extraction results from 72 hour bottle roll tests
conducted by Kappes Cassiday & Associates on -200 mesh material
and with initial gravity concentration and cyanidization of the
tailings material. (The Hazen Research results on -10 mesh
material are included for comparison)
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Calculated Au Extracted Au Extracted @ 200 mesh Grav Con
Head, @10 mesh @ 200 mesh + Grav Grade
Sample # gms Au/MT % % % gms Au/MT
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100112113 0.459 79% 84% 92% 45.90
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100588589 1.686 59% 73%
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100772773 0.728 76% 70%
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100829830 1.278 77% 83% 91% 129.12
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101024026 0.620 71% 88%
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101273274 0.787 78% 87% 91% 54.80
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101291292 1.333 87% 91% 94% 94.37
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101548549 2.670 95% 94% 99% 163.80
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101604605 0.992 75% 83% 96% 200.24
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101774775 1.069 85% 94% 95% 89.78
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101827829 2.733 80% 98% 94% 77.32
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101847849 1.279 58% 59% 82% 67.34
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102070071 0.594 92% 87%
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102096097 1.074 71% 89% 85% 50.58
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102575576 0.927 96% 94% 98% 200.09
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102642643 0.596 69% 80% 91% 47.59
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102886887 0.873 36% 42% 75% 81.92
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103110111 0.711 75% 85% 95% 153.51
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Average OX &
Trans Ore 76% 82% 91% 104.03
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102536537 0.875 90% 96% 99% 50.58
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100123124 0.609 59% 76% 90% 27.08
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101896897 1.269 28% 41% 70% 52.68
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101925926 1.552 48% 64% 85% 194.67
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101618619 1.434 60% 80% 90% 68.00
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101437438 0.819 59% 70% 85% 37.30
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Average UN-OX
Ore 57% 71% 87% 71.72
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Overall Deposit
Average 66% 77% 89% 87.87
Twenty-four samples were ground to -200 mesh and then split, with one portion undergoing whole ore bottle roll testing and the other portion going to a gravity concentrator. Only 20 samples had sufficient material to do both tests. The whole ore bottle roll tests were conducted on 1 kilogram aliquots with 40% solids in 1 gram/litre cyanide mixture. During the test, samples were extracted at 2, 4, 8, 16, 24, 36, 48 and 72 hours to define an extraction curve. The gravity concentration test involved feeding the sample through a Falcon SB40 Concentrator at 3 psig, 50 Hz and 20% solids three times. Following the first two runs, the Falcon concentrate was hand panned and the middling returned to the tails for further concentration. The final run concentrate was panned and the middlings separated. The combined panned concentrate and final middlings were subsequently fire assayed while the tails were subjected to 72 hour bottle roll cyanide extraction. The combined assays were used to calculate the total gold recovery.
Approximately half of the material included in the January 2009 resource estimate is classified as Oxidized/Transitional. This ratio was used to estimate an overall average recovery for the Livengood deposit of approximately 89% for the -200 mesh, gravity concentrate plus cyanide leached tails group. The Company is currently in the process of expanding its metallurgical sample database to represent the southern and recently defined south-western and north-eastern extensions of the Livengood mineralization. These samples will be submitted for testing following completion of the current winter drilling program.
Qualified Person
Jeffrey A. Pontius (CPG 11044), a qualified person as defined by National Instrument 43-101, has supervised the preparation of the scientific and technical information that forms the basis for this news release and has approved the disclosure herein. Mr. Pontius is not independent of ITH, as he is the President and CEO and holds common shares and incentive stock options.
The work program at Livengood was designed and is supervised by Dr. Russell Myers, Vice President, Exploration, and Chris Puchner, Chief Geologist (CPG 07048), of the Company, who are responsible for all aspects of the work, including the quality control/quality assurance program. On-site personnel at the project photograph the core from each individual borehole prior to preparing the split core. Duplicate reverse circulation drill samples are collected with one split sent for analysis. Representative chips are retained for geological logging. All sample shipments are sealed and shipped to ALS Chemex in Fairbanks, Alaska for preparation and then on to ALS Chemex in Vancouver, B.C. for assay. ALS Chemex's quality system complies with the requirements for the International Standards ISO 9001:2000 and ISO 17025: 1999. Analytical accuracy and precision are monitored by the analysis of reagent blanks, reference material and replicate samples. Quality control is further assured by the use of international and in-house standards. Finally, representative blind duplicate samples are forwarded to ALS Chemex and an ISO compliant third party laboratory for additional quality control.
About International Tower Hill Mines Ltd.
International Tower Hill Mines Ltd. is a resource exploration company, focused in Alaska and Nevada, which controls a number of exploration projects representing a spectrum of early stage to advanced gold and base metal discoveries. The Company's 100% owned Livengood deposit is an advanced bulk tonnage resource expansion project that is the current focus of its Alaskan program. ITH is committed to building shareholder value through new discoveries while maintaining a majority interest in its holdings, thereby giving its shareholders the maximum value for their investment.
On behalf of INTERNATIONAL TOWER HILL MINES LTD.
Jeffrey A. Pontius, President and Chief Executive Officer