Midway Gold Corp. ("Midway") continues to find excellent gold recovery results for its Spring Valley gold project, Pershing County, Nevada. Test results report gold recoveries up to 98% with conventional oxide ore leaching treatment, and showed high gold recoveries across all the grade ranges tested.
These tests were conducted at McClelland Laboratories Inc., Reno, Nevada, and were overseen by Barrick Gold Exploration Inc., a wholly owned subsidiary of Barrick Gold Corporation (NYSE:ABX, TSX:ABX), Midway's earn-in partner at Spring Valley.
“These positive metallurgical results speak well for the high quality of this gold resource at Spring Valley. The results show that several commonly used production options exist for processing and recovering the gold from Spring Valley and these include heap leaching, typical oxide leaching and recovery by gravity methods.”
Ken Brunk, President and COO of Midway said: "These positive metallurgical results speak well for the high quality of this gold resource at Spring Valley. The results show that several commonly used production options exist for processing and recovering the gold from Spring Valley and these include heap leaching, typical oxide leaching and recovery by gravity methods."
Thirteen composite samples representing oxide, transition and reduced ores were tested by column leaching, bottle roll and gravity methods. Grades of the composite samples ranged from 0.21 grams per tonne (gpt) to 5.07 gpt (0.006 ounces per ton - "opt" to 0.148 opt1); nine of the samples had grades less than 1.03 gpt (0.030 opt). Because coarse gold is known to be present at Spring Valley, the reported gold grades were determined by metallic screen fire assays.
Column Leach Tests
Column leach tests simulate heap leach conditions, and these tests conducted over 260 days yielded gold recoveries from 46% to 98% and average 73%. Individual results for the oxide, transition and reduced ores averaged 77%, 80% and 68% respectively. Rocks tested by column leach methods were crushed such that 80% of the rocks were less than 12.7 millimeters (one-half inch) in diameter.
Bottle Roll Tests
Bottle roll tests were conducted for 96 hours on ores ground to minus 300, 150, and 75 microns (48, 100 and 200 mesh sizes); these recoveries were 91%, 94% and 95% respectively.
Gravity Tests
Gravity test recoveries ranged from 78% to 97% and averaged 86%. The tests were conducted on ores at 850, 212, 150, and 75 microns (20, 65, 100 and 200 mesh sizes). The tests used a Knelson concentrator; more than half of the recovered gold was coarser grained than 850 and 212 microns (20 and 65 mesh size screens).
Spring Valley is a large gold project covering 18.4 square miles and located about 20 miles northeast of Lovelock, Nevada. Spring Valley currently has an Inferred Resource of at least 1.8 million ounces of gold in 79.61 million tonnes grading 0.72 gpt (0.021 opt). (See the Midway press release dated March 2, 2009 and the subsequent NI 43-101 Technical Report filed on SEDAR March 30, 2009.) Midway and Barrick entered into an agreement on March 9, 2009 for the exploration and development of the Spring Valley project. Under the terms of the agreement, Barrick may earn a 60% interest in the project by spending US$30 million in work expenditures before December 31, 2013.
Data reported to Midway by Barrick and disclosed in this press release has been reviewed for Midway by Richard D. Moritz, (B.Sc., MBA), a "qualified person" as that term is defined in National Instrument 43-101.
1 Conversion factor: 1 ounce per short ton equals 34.2857 grams per tonne.
Source: Midway Gold Corp.