Exeter's testwork recovers high grades from La Cabeza
2006-01-26 08:49 ET - News Release
Mr. Bryce Roxburgh reports
LA CABEZA PRODUCES HIGH GOLD RECOVERIES IN METALLURGICAL TESTWORK
Exeter Resource Corp. has provided the latest results of metallurgical testing on its La Cabeza gold project. Results confirm high gold and silver recoveries using a conventional gravity separation circuit and carbon in leach flowsheet.
Yale Simpson, Exeter's chairman said: "This program was a comprehensive determination of the metallurgy of the principal ore types at La Cabeza. Testwork confirmed that overall recoveries of 91 per cent of gold and 80 per cent to 85 per cent of silver are realistic for the financial modelling of the La Cabeza mine.
"In addition, the mineralization is confirmed to be free-milling and clean -- the gold is readily liberated by entirely conventional gravity/leaching circuits. Gravity gold recovery alone averaged 30 per cent, but exceeded 50 per cent on some samples. Furthermore, the ores are consistently very low in pyrite and base metals, which is particularly positive from an environmental perspective."
Details of metallurgical testing
The test programs were carried out at: Metcon Pty. Ltd. of Sydney, Australia (a member of the AMMTEC group); AMMTEC Ltd. of Perth, Western Australia; Outokumpu Technology Pty. Ltd. of Perth, Western Australia; and Knight Piesold Pty. Ltd. of Perth, Western Australia. The program included optical mineralogy, comminution, flotation, gravity separation, cyanide leaching and tailings characterization testwork.
The testwork was carried out on relatively coarsely ground, 95-micron, material taken from individual mineralized intercepts and composites prepared from diamond drill cores selected from the 2004 drilling program. The head assays of composite samples from each of the main ore zones were as follows:
Assay Ojo Luna Cuello Bulk
Gold (g/t) 9.43 3.13 7.93 5.78
Silver (g/t) 6.9 18.3 61.3 25.8
Sulphur (%) 0.10 0.16 0.47 0.28
Iron (%) 1.50 1.27 1.24 1.26
Arsenic (ppm) 4,320 105 80 1,235
Copper (ppm) 38 28 26 27
Lead (ppm) 35 32 19 28
Zinc (ppm) 78 33 55 52
Specific outcomes from the testwork included:
grind size: 95 microns;
carbon in leach (CIL) pulp density: 45 per cent solids;
gravity circuit recovery 30 per cent to 50 per cent;
CIL gold recovery 93 per cent to 94 per cent on the bulk composite;
gold recovery variability on deposit composites: 92.7 per cent to 93.9 per cent;
gold recovery variability on individual mineralized intercepts: 80 per cent to 97 per cent -- average 91 per cent;
silver recovery variability on individual mineralized intercepts: 80 per cent to 85 per cent; and
reagent consumption (CaO and NaCN) approximately 0.40 kilogram per tonne of ore.
The La Cabeza ores are characterized as hard and abrasive, similar to those of other South American epithermal gold deposits. Leach tailings settling rates were fast and densities approaching 65 per cent solids were achieved from continuous settling tests. Specific settling rates were 0.7 tonne per square metre per hour.
The Exeter website provides additional disclosure of test results.
Jerry Perkins, FAusIMM (CPmet), Exeter's vice-president development and operation, and a qualified person within the definition of that term in National Instrument 43-101, Standards of Disclosure for Mineral Projects, has supervised the preparation of the precious metal metallurgical and development information contained in this news release
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