Corvus Gold Inc. has released new results from its 2014 metallurgical testing program at the North Bullfrog project in Nevada. Bottle roll tests have been performed on five composite samples developed from PQ core drilled during exploration of the Yellowjacket vein system during 2013. The composites were designed to represent the various types of mineralization associated with the Yellowjacket vein system and to provide information on metallurgical recovery using cyanide leach processing.
The results are presented in the tables and indicate high gold and silver recovery at particle sizes typical of cyanide leach milling systems in Nevada. The measured recoveries of both metals at larger particle sizes (greater than 80 per cent minus 1.7 millimetres) were lower, indicating that mill processing would likely enhance recoveries for most of the Yellowjacket mineralization.
GOLD RECOVERY FROM YELLOWJACKET COMPOSITE SAMPLES IN 96-HOUR BOTTLE ROLL TESTS 80%-19mm 80%-6.3mm 80%-1.7mm 80%-0.15mm 80%-0.11mm 80%-0.075mm Composite (3/4 inch) (1/4 inch) (12 mesh) (100 mesh) (150 mesh) (200 mesh) YJPQ01 12.7% 30.4% 50.0% 86.2% 88.4% 88.3% YJPQ02 11.3% 32.9% 53.6% 92.0% 92.9% 90.4% YJPQ03 13.7% 27.3% 45.9% 88.5% 88.3% 89.6% YJPQ04 23.1% 33.3% 57.8% 61.4% 67.3% 68.8% YJPQ05 43.9% 44.2% 54.0% 76.4% 76.2% 74.4%
SILVER RECOVERY FROM YELLOWJACKET COMPOSITE SAMPLES IN 96-HOUR BOTTLE ROLL TESTS 80%-19mm 80%-6.3mm 80%-1.7mm 80%-0.15mm 80%-0.11mm 80%-0.075mm Composite (3/4 inch) (1/4 inch) (12 mesh) (100 mesh) (150 mesh) (200 mesh) YJPQ01 10.5% 24.9% 46.9% 66.8% 68.7% 70.3% YJPQ02 15.0% 35.4% 50.2% 74.3% 75.8% 77.4% YJPQ03 11.4% 20.5% 38.4% 68.4% 65.9% 76.1% YJPQ04 16.7% 41.9% 52.3% 62.0% 66.0% 66.7% YJPQ05 29.4% 36.8% 47.4% 65.0% 70.0% 61.9%
Cyanide consumptions ranged from less than 0.07 to 0.2 kilogram per tonne and lime consumptions ranged from 0.5 to 2.5 kilograms tonne across the different tests, generally increasing with reduced particle size.
The composites were designed to be representative of the range of mineralization types and grades observed in the Yellowjacket vein system and are listed below:
- Composite YJPQ01 was made up of quartz vein material with an average calculated head grade (extracted gold plus gold remaining in the tail) of 6.7 grams per tonne gold.
- Composite YJPQ02 was composed of vein breccia (about 30 per cent quartz) and stockwork (less than 10 per cent quartz) and had an average calculated head grade of 5.8 grams per tonne gold.
- Composite YJPQ03 was constructed of vein breccia and stockwork samples with an average calculated head grade of 1.8 grams per tonne gold.
- Composite YJPQ04 was constructed of samples with 5 to 10 per cent quartz veining and had an average calculated head grade of 0.56 gram per tonne gold.
- Composite YJPQ05 was constructed entirely of stockwork and had an average calculated head grade of 0.46 gram per tonne gold.
Further metallurgical testing of the Yellowjacket composite samples is under way to develop information on the potential for gravity gold recovery followed by agglomeration of the tailings on to the heap leach material from the disseminated resources for final recovery on the leach pad, a common processing system currently in use in Nevada.
Preliminary economic assessment status
The company also wishes to confirm that, with the release of the new estimated mineral resources for the NBP, effective March 25, 2014, there is no longer a current preliminary economic analysis for the NBP and the previous preliminary economic assessment for the NBP released on Oct. 28, 2013, is no longer valid.
About the North Bullfrog project, Nevada
Corvus controls 100 per cent of its North Bullfrog project, which covers approximately 68 square kilometres in southern Nevada. The property package is made up of a number of private mineral leases of patented federal mining claims and 758 federal unpatented mining claims. The project has excellent infrastructure, being adjacent to a major highway and power corridor as well as a large water right.
Based upon a $1,300 (U.S.) gold price and a silver to gold price ratio of 59:1, the North Bullfrog project currently has estimated mineral resources defined in six deposits: the structurally controlled Yellowjacket milling deposit and the oxidized disseminated heap leach Sierra Blanca, Jolly Jane, Air Track West, Connection and Mayflower deposits. The Yellowjacket vein-style deposit has an indicated mineral resource of 3.69 million tonnes at an average grade of 1.03 grams per tonne gold and 5.52 grams per tonne silver for 122,000 contained ounces of gold and 654,000 ounces of silver and an inferred mineral resource of 18.40 million tonnes with an average grade of 0.94 gram per tonne gold and 6.16 grams per tonne silver for 555,000 contained ounces of gold and 3.64 million ounces of silver, both at a 0.29-gram-per-tonne gold cut-off.
The five oxidized disseminated heap leach deposits contain an indicated mineral resource of 25.72 million tonnes at an average grade of 0.29 gram per tonne gold for 240,000 contained ounces of gold and an inferred mineral resource of 185.99 million tonnes at 0.19 gram per tonne gold for 1,136,000 contained ounces of gold (both at a 0.13-gram-per-tonne gold cut-off), with appreciable silver credits.
For full details with respect to the assumptions underlying the current resource estimate detailed herein, and listing of all of the metallurgical testing data please review the company’s latest National Instrument 43-101 technical report entitled “Technical Report — The North Bullfrog Project, Bullfrog Mining District, Nye County, Nevada,” dated April 1, 2014, and available on SEDAR or at the company’s website.
Qualified person and quality control/quality assurance
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 Corvus, as he is the chief executive officer, and holds common shares and incentive stock options.
Carl E. Brechtel, Nevada PE 008744 and registered member 353000 of SME, a qualified person as defined by National Instrument 43-101, has supervised execution of the work outlined in this news release and has approved the disclosure herein. Mr. Brechtel is not independent of Corvus, as he is the chief operating officer, and holds common shares and incentive stock options.
The work program at North Bullfrog was designed and supervised by Russell Myers, CPG 11433, president of Corvus, and Mark Reischman, Corvus’s Nevada exploration manager, who are responsible for all aspects of the work, including the quality control/quality assurance program. On-site employees at the project log and track all samples prior to sealing and shipping. Quality control is monitored by the insertion of blind certified standard reference materials and blanks into each sample shipment. All resource sample shipments are sealed and shipped to ALS Minerals in Reno, Nev., for preparation and then on to ALS Minerals in Reno or Vancouver for assaying. ALS Minerals’ 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. Finally, representative blind duplicate samples are forwarded to ALS Chemex and an ISO-compliant third party laboratory for additional quality control.