Clifton Star Resources Inc. ("Clifton Star" or the "Corporation") is pleased to report that it has successfully completed a continuous pilot plant test at SGS Minerals at Lakefield, Ontario, Canada. The tests and analyses were carried out from March to August 2013 to confirm gold recoveries using flotation, pressure oxidation and cyanidation. The tests were highly successful and confirmed earlier bench results.
Highlights: Continuous flotation pilot plant testing was conducted to make a Bulk Concentrate for Pressure Oxidation (POX) pilot testing and also, as an alternate process, to simply produce a High Grade Gold Concentrate that could be sold directly to Smelters.
For the POX process, the Bulk Concentrate produced by flotation assayed 26.8 g/t Au with an average 91.7% gold recovery. After applying POX to the flotation concentrate and cyanide leach to the flotation tailing, the overall average recovery of gold was 92%. Further work has shown that this can reach 94% by using a hot lime treatment of the POX product before cyanidation.
For the Gold Concentrate process, the concentrate assayed an average of 49.9 g/t Au, 50.0 g/t Ag and 31.4% S. Flotation recoveries averaged 86.5% for gold. The flotation tailing was cyanide leached and this raised the overall gold recovery to 91.9%. These concentrates could likely be sold, without further processing to Smelters.
Duparquet Bulk Sample Pilot Tests:
A 12 tonne composite sample of Duparquet mineral sample was prepared by Clifton Star under the supervision of Louis Martin, P.Geo., VP Exploration, and shipped to SGS Minerals. The material was representative of the contribution of the various zones to the Duparquet resource estimate, with a target grade typical of the average grade for the various zones. The pilot plant sample graded 1.835 g/t Au, 2.2 g/t Ag, 1.16 % S and 0.055 % As.
The SGS Pilot Plant was arranged using suitable equipment to simulate a full scale mineral processing plant. The pilot plant received crushed material, which was then continuously ground in a ball mill to approximately 100 micron particle size (P80) and then floated to produce a concentrate enriched in gold and sulfur. The flotation consisted of rougher and cleaner flotation. The flotation of Bulk Concentrate for the POX process required one stage of cleaning. The flotation for the production of the High Grade Gold Concentrate process required two stages of cleaning and an intermediate regrinding step to improve mineral liberation.
The flotation tailings were collected separately from the concentrates. The flotation tailings were tested by cyanidation to determine what additional gold recovery could be obtained. The tailings also underwent environmental characterization and cyanide destruction. Tests for tailing sedimentation were also carried out.
A separate program of testing on crushing and grinding was also carried using a portion of the bulk sample. It included a study of High Pressure Grinding Rolls (HPGR) as part of the comminution strategy. The study will enable Clifton to choose the crushing and grinding parameters best suited for the Duparquet mineralized zones.
For the POX process, the Bulk Concentrate produced assayed 26.8 g/t Au. and flotation recoveries averaged 91.7% Au. After applying POX and cyanide leach to the flotation tailing, the overall recovery of gold was 92%. Further work has shown that this can reach 94% by using a hot lime treatment of the POX product before cyanidation.
For the Gold Concentrate process, the concentrate assayed an average of 49.95 g/t Au, 50.05 g/t Ag and 31.4% S. Flotation recoveries were 86.5% for gold. The flotation tailing was cyanide leached and raised the overall gold recovery to 91.9%. These concentrates could likely be sold, without further processing, to Smelters.
The results confirms prior tests carried out in 2012, and will be incorporated in the ongoing Pre-Feasibility Study on the Duparquet project, due for release in Q1, 2014.
Dr. David Dreisinger, P.Eng., F.C.I.M., F.C.A.E., is the Qualified Person (NI 43-101) who supervised the preparation of the technical information in this news release. Dr. Dreisinger is Professor and Chairholder, Industrial Research Chair in Hydrometallurgy at the University of British Columbia (Vancouver, Canada) and consults to the worldwide metallurgical industry through Dreisinger Consulting Inc.