| 1 | o Testwork shows that 94% and 93.6% gold is recoverable in the Dubbo |
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| 2 | and Mystery samples respectively using this process; |
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| 3 | o Only environmentally benign reagents are used to achieve these |
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| 4 | recovery levels; |
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| 5 | o Design of pilot plant is underway. |
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| 6 | |
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| 7 | Testwork Overview |
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| 8 | Gold at the Talisman Mine is hosted in three major quartz veins, namely, the |
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| 9 | Maria, Mystery and Crown/Welcome. Of these three the Maria vein is the major |
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| 10 | contributor containing approximately 91% of the mines 469,000 Oz AuEq Mineral |
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| 11 | Resource within the Dubbo, Bonanza and Woodstock Zones. The average grade of |
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| 12 | the resources in these zones is estimated at 22.0g/t, 23.6g/t and 6.3g/t AuEq |
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| 13 | respectively with some 313,000 Oz lying in the Dubbo Zone. (please see |
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| 14 | announcement of |
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| 15 | https://www.asx.com.au/asxpdf/20170905/pdf/43m2d5v2hnybjc.pdf) Exploration in |
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| 16 | this area has yielded some spectacular results, notably hole BM 37 which |
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| 17 | yielded 1.8 m @ 656g/t Au and 2080g/t Ag. |
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| 18 | The Mystery Vein is a newly discovered vein that is highly prospective and a |
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| 19 | potentially significant contributor to the future of the mine. |
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| 20 | The metallurgical testwork was designed to deliver reliable and repeatable |
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| 21 | results which will be used to inform engineering studies and cost estimates |
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| 22 | both for pilot testwork during the Bulk Sampling Project and to inform design |
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| 23 | in an updated Pre-Feasibility Study. |
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| 24 | Testwork examined the processing path, post mining, as illustrated below: |
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| 25 | |
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| 26 | There are four stages to the metalurgical process once ore has been mined and |
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| 27 | crushed to a suitable feed size: |
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| 28 | 1) Grinding of ore to a suitable size to liberate gold; |
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| 29 | 2) Recovery of free milling gold in a gravity concentrator |
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| 30 | 3) Flotation of the concentrator tails to recover additional gold |
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| 31 | 4) Final recovery of gold from concentrate |
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| 32 | |
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| 33 | Processing - Grinding |
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| 34 | |
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| 35 | An important output from the testwork was to determine the optimal grind size |
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| 36 | to liberate gold contained in the ore. Grinding (or milling) of ore takes |
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| 37 | place in a ball mill and is the most expensive and energy intensive part of |
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| 38 | the process. The finer the grind size required the more energy and time is |
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| 39 | taken up. Two grind sizes were tested here with ore initially milled to p80 |
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| 40 | passing 106?m and again to p80 passing 53?m. |
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| 41 | |
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| 42 | Processing - Gravity Concentration |
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| 43 | |
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| 44 | The milled product was pulped to 50 % solids and the resultant pulp was |
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| 45 | subjected to gravity concentration via a Knelson Centrifugal Concentrator. |
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| 46 | The primary concentrate was upgraded via careful hand panning to provide |
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| 47 | final concentrate mass yield approaching that of operating Knelson |
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| 48 | installations. Final free gold concentrate (pan concentrate) was assayed via |
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| 49 | total fusion to eliminate sampling error and nugget effect. Secondary |
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| 50 | concentrate (pan tailing) and final tailings were dried, weighed and split |
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| 51 | for Au assay. |
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| 52 | Results from this show that 61.3% of gold in Dubbo ore, and 81.9% of gold in |
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| 53 | Mystery ore can be recovered directly through this process. |
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| 54 | Processing - Flotation |
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| 55 | |
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| 56 | Tailings from the gravity concentrator were pulped to 20% solids and |
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| 57 | subjected to single stage flotation with the addition of copper sulphate, |
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| 58 | sodium isobutyl and Dow 250 which are all environmentally benign reagents. |
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| 59 | This process resulted in recovery of an additional 32.7% of gold from Dubbo |
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| 60 | ore and 11.7% from Mystery ore, yielding overall recoveries of 94% and 93.6% |
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| 61 | respectively. Variance of recovery rates between the two grind sizes was |
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| 62 | insignificant. This is comparable to the recovery achieved from Talisman ore |
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| 63 | which has previously been treated using a cyanide leach process. Importantly, |
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| 64 | the gravity and flotation process will produce inert tailings with low |
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| 65 | sulphide levels. |
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| 66 | |
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| 67 | Processing - Gold Recovery |
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| 68 | |
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| 69 | On exit from the flotation tanks the concentrate can either be sold directly |
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| 70 | on the market or the gold recovered on a shaker table and smelted. |
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| 71 | These results are very pleasing with recovery rates nearing those attained |
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| 72 | from similar tests involving cyanide leaching. Essentially this means that, |
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| 73 | following pilot testing, the company will be able to use only environmentally |
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| 74 | benign reagents for gold recovery which supports the company in its goal for |
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| 75 | the Talisman Mining operation to be a responsible, environmentally |
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| 76 | sustainable operation. |
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| 77 | Chief operating officer and principal mining engineer Wayne Chowles said "The |
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| 78 | results of this testwork provides the necessary hard data with which to |
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| 79 | proceed with forward planning and takes us an important step closer to |
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| 80 | realizing the potential of this magnificent orebody |
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