Metallurgy

Leach Testwork

MRA Consultants (MRA), through George Shadford, Metallurgical Engineer, arranged early cyanidation leach amenability testwork in 1998 by Oretest Pty Ltd (now SGS Lakefield) in Perth, Western Australia. Tests were carried out on assay reject pulps from 13 drill core reject samples of Tambang, a silver/gold-carbonate-base metal association in a vein system, and 16 drill core reject samples of Jambi, an oxide hosted gold and silver deposit.

Jambi assay reject pulp samples submitted for leaching were said to be fully oxidized, except for two samples with minor pyrite. Head assays ranged from 1 to 34 g/t Au and 1 to 551 g/t Ag. Base metal contents were said to be low. Jambi gold extractions were 94 to 100% on samples with a head assay of greater than 3 g/t, and 60 to 85% on samples of less than 3 g/t. Preg robbing was suspected with two of the higher gold samples. Gold extraction was largely complete after 24 hours, except for two samples which required 48 hours. Silver extraction was 50 to 97% except for two samples which yielded less than 12% extraction. Cyanide consumption was said to be reasonable for all tests. Lime consumption was reported to be generally low except for several tests where it was found to be particularly high.

The Jambi samples were found to be amenable to silver and gold leaching. The lower grade was considered to show potential for heap leaching and the higher grade potential for carbon-in-pulp leaching.

The Tambang assay reject pulp samples submitted for leaching at Oretest were of widely varying precious metal and base metal head grades including 0.3 to 5.0 g/t Au (mainly less than 1 g/t Au), 7 to 580 g/t Ag, 18 to 8,710 ppm Cu, 51 to 85,000 ppm Pb, 800 to 36,000 ppm Zn, 12 to 2,000 ppm Sb and 27 to 550 ppm As. Tambang gold extractions varied from 23 to 94%, with the lower gold extractions being considered due to sulphide locking or oxygen deficiency in some but not all tests. Silver extractions varied from 2 to 89%, with the lower silver extractions potentially associated with manganese minerals or other factors not identified.

More recent leach testwork was carried out in October 2006 by Intertek of Jakarta. Bottle roll cyanide leach tests were conducted on fresh drill hole samples provided by Finders Resources. The Tambang samples were taken from 4 drill holes at depths of 35 to 190 metres. Average precious metal head assays were 1.08 g/t Au and 202 g/t Ag. Head assays in the upper zone above 44 metres varied from 0.2 to 6 g/t Au, 6 to 900 g/t Ag, 1 to 32% Mn, 0 to 2% Pb and 0 to 0.6% Zn. Head assays in the lower zone from 80 to 190 metres varied from 0.2 to 1.4 g/t Au., 12 to 180 g/t Ag, 1 to 34% Mn, 0 to 1.5% Pb and 0 to 7.6% Zn. Assay variability was broadly in line with that reported earlier by MRA.

Jambi samples for Intertek testwork were taken from 8 drill holes at depths of 9 to 98 metres. Average precious metal head assays were 2.0 g/t Au and 26 g/t Ag. Individual head assays varied from 0.3 to 5.8 g/t Au and from 0 to 162 g/t Ag, or generally similar to the variability reported earlier by MRA.

The Intertek bottle roll method CN04 appears to have consisted of 0.25% NaCN concentration at a pH >10.0 in a 35% solids pulp at minus 200 mesh grind size for up to 36 hours with cyanide additions at 4, 8, 12, 24 and in some cases also at 36 hours. Cyanide consumption increased rapidly with leach time for Tambang from an average of 2 kg NaCN/tonne solids at 4 hours to 6.5 kg /tonne solids at 12 hours. For Jambi, the average cyanide consumption was much lower, and increased from 1.0 kg NaCN/t solids at 4 hours to 2.8 kg NaCN/t solids at 12 hours.

Intertek Tambang bottle roll gold extraction averaged 54%, but varied widely from 10 to 80% at depths of 80 to 190 metres and from 65 to 100% at 30 to 50 metres. Silver extraction averaged 41% and varied from 10 to 90% at depths of 80 to 190 metres and from 10 to 41% at 30 to 50 metres.

Intertek Jambi bottle roll gold extraction averaged 89%, with all recoveries exceeding 90% except for the samples at 81-100m depth which varied from 30 to 87%. Silver extraction averaged 41% but varied from below 10% to in excess of 90%.

In general many of the Tambang samples were considered refractory for gold and silver extraction.

Flotation Testwork

G&T Metallurgical Services Ltd (G&T) of Kamloops, Canada have recently proposed a two phase program for scoping mineralogy and flotation testwork on approximately 150 kg of fresh half drill core from the Tambang resource. The first phase will concentrate on defining flowsheet and reagent conditions for a simple lead-zinc sequential flowsheet for a master composite. Work scope will include grind size selection from a modal analysis at a P80 grind size of 100 microns, Bond ball mill determination, 5 rougher tests, 5 cleaner tests and a minor element scan on the concentrates. The second phase will assess the variability of metallurgical response of 16 sub-composites using the developed flowsheet. Work scope will include head assays, mineral speciation, comparative work index and batch cleaner tests.