Alvo Minerals Limited announced preliminary metallurgical test work results from a bulk sample of mineralized Volcanogenic Massive Sulphide (VMS) samples from the C3 prospect of the Palma Project ("Palma" or "the project").
Alvo prepared and sent over 315kg of diamond core in 202 individual samples from the C3 prospect in Central Brazil to Auralia Metallurgy (a specialist in minerals flotation) in Perth, Australia. The samples were selected and received under the supervision of BHM Process Consultants ("BHM"), specialists in Metallurgical test work management and supervision. The samples were received and logged, composited and the preparation of a master composite was completed. The master composite was selected to approximately match the overall expected grade of the C3 VMS mineralized zone. The sample was initially tested with a 2-stage rougher flotation at P80 125m, 106m and 75m and the results analyzed for future work. The finest of the rougher tests (P80 at 75m) was chosen for single-pass Rougher and Cleaner stage Flotation tests as illustrated in the test work flowsheet. The various samples were sent to the Nagrom independent laboratory for assaying. Results were received from these tests are reported. Two concentrates were successfully separated, with the Copper and Lead reporting to the first bulk sulphide concentrate containing grades of 25.2% Cu, 3.35% Pb, 1.84% Zn, 246g/t Ag, 0.9g/t Au. The recovery of the Cu to this concentrate was >70%, however there is significant metals in the tails which may be recovered during additional test work (there was only 1.6% of the Cu rejected in the rougher tails). A calculated projected recovery to this concentrate for the Cu (to be confirmed by locked cycle tests currently underway) is 81.1% Cu, at >20% Cu grade. The second concentrate was a Zinc Concentrate which reported a grade of 46.2% Zn, 1.93% Cu, 0.25% Pb, 0.12 g/t Au and 20 g/t Ag. The recovery of the Zn to this concentrate was >56%, however there is significant metals in the tails which may be recovered during additional test work. Overall assumed recovery of the Zn in this concentrate (to be confirmed by locked cycle tests currently underway) is estimated 82.3% Zn at >50% Zn grade. The ongoing locked cycle test work will better estimate the final concentrate grades and recoveries as the cleaner tails are re-circulated. This will allow for the metal in the system to either report to a concentrate or final tailings. The deportment of Au & Ag to the rougher tails is relatively low at 12% & 27.7%, however the feed grades are relatively low at 0.09ppm Au and 24.2ppm Ag. The arsenic rejection to the rougher tail is significant at ~67%. The grades observed in the final concentrates are well below normal penalty specifications, however, as the target metal recoveries increase in a locked cycle, the values of the As and other metals may increase. No product marketing of the concentrates has been completed to date, however based on industry standards these concentrate grades are considered attractive, particularly the copper and lead concentrate. Optimization is ongoing to elevate the zinc concentrate to >50 % contained Zn. The Company requested BHM undertake a concept review of generating sulphuric acid from the tailings using known processing, as a way of increasing sustainability credentials, mitigating environmental risk and adding another potential revenue stream to the project. BHM have reported that, assuming the grade of the tailings is similar to the C3 master composite generated from the test work described above. The conversion of sulphur to sulphuric acid is exothermic and the gasses produced may be suitable for heat recovery and used to generate power. BHM also reported that one of the by-products may be high-grade iron ore (blend of hematite and magnetite), which may also be saleable. Test work will be initiated to test this theory in addition to desktop work to understand the typical capital and operating costs of "off-the-shelf" sulphuric acid plants. Auralia Metallurgy also completed a Bond Mill closed circuit grind ability test on the C3 master composite sample. The open test aperture for this sample was 106m and the resultant Bond ball mill work index was 14.0 (kilowatt hours/dry tonne). On the standard scale of material property, this is considered Medium-Hardness and relatively soft compared to other VMS projects.