Announcement • Jun 22
Omai Gold Mines Corp. Reports Positive Metallurgical Testwork Results for Wenot and Gilt Deposits At Omai Gold Project
Omai Gold Mines Corp. announced results from its first phase of metallurgical testwork on the Wenot and Gilt deposits at its 100% owned Omai Gold Project in Guyana, South America. High gold extraction was achieved from testwork with 93% gold extraction at 1.0 g/t Au to 95% Au extraction at 3.2 g/t Au, from a material grind size of 80% passing 75 microns. Gold dissolution rates were rapid with a 32-hour retention time determined as optimal. Both Wenot and Gilt deposit mineralogies are clean with no deleterious components (no organic carbon, tellurides, or antimony) and with very low soluble copper, lead or zinc content. The upcoming Preliminary Economic Assessment will incorporate conventional milling and processing through a carbon-in-leach plant for extraction of gold for the Omai deposits. The objective of this Phase 1 metallurgical testwork was to determine the amenability of the Wenot and Gilt gold deposits to a standard bottle roll leach and carbon-in-leach circuit. A total of 72 representative composite samples totalling 558 kilograms were evaluated by SGS (Canada) in Lakefield, Ontario (Canada), comprised of 61 samples from the Wenot deposit and 11 from the Gilt deposit. This First Quarter-Second Quarter 2026 metallurgical test program delivered favourable results from both the Wenot and Gilt deposit composite samples. Gold extraction from the fresh rock averaged 93% at a head grade of 1.0 g/t Au and increased to a maximum of 95% at 3.2 g/t Au. Samples were subjected to bottle roll leach at 45% solids slurry density and a grind size of 80% passing 75 microns. Retention time studies for gold extraction included rate kinetic solution samples taken at 4, 8, 12, 24, and 36 hours for gold analysis. Testing indicated 85% dissolution after 12 hours, 95% after 24 hours, and 97% to 98% of ultimate metal extraction after 32 hours. A 32-hour retention time has been selected for initial project design. Grind size versus metal extraction comparisons were pursued on selected samples which confirmed 80% passing 75 microns as an appropriate target and design point. Minimal gains in metal extraction were achieved at a finer grind size, while the pursuit of a coarser grind size resulted in a measurable decrease in gold extraction. The operation of interstage carbon screens in carbon-in-leach will constrain product grind size in a typical range of 80% passing 75 to 106 microns. Process solutions were notably clean, with low levels of copper, zinc, and lead. The primary leach consumer is iron sulphides which is advantageous since the product is relatively easy to precipitate and remove with leach solution water treatment. No organic carbon was identified, even within Wenot's sediment-hosted gold zones, therefore there are no indications that gold extraction from these zones will be impeded. The 72 composite samples were selected to evaluate a wide range of composite sample head grades (0.6 g/t to 15.8 g/t Au) and included 16 individual or mixed lithologies. A total of 759m of core, from 23 diamond drill holes, were included within the composite samples. The Gilt deposit, being intrusion-hosted, is relatively homogeneous and has limited lithologic variation and as such, a total of 11 composites were considered sufficient to reflect potential variations. For the Wenot deposit, the gold mineralization is hosted within multiple zones of highly variable lithologies. To test for possible metallurgical variability, a total of 61 samples were taken from 22 Wenot drill holes spanning almost 1,600 metres along the strike of the deposit, within a wide range of mineralized lithologies and at differing depths. As a component of QA/QC for metallurgical test work, each composite sample was assayed and compared with the calculated weighted grade from exploration drill program sampling. The correlation between the exploration drill core assays and metallurgical head grades is very good with a small number of outliers, likely due to the presence of coarse gold grains. Project definition studies to date for Omai support a conventional process plant flowsheet built around primary crushing, followed by a grinding circuit consisting of a Semi-Autogenous Grinding mill, ball mill, and pebble crushing (together an SABC grinding circuit). Based on the initial testwork, the circuit would be designed to achieve a target grind size of 80% passing 75 microns before feeding into a carbon-in-leach circuit. The proposed downstream circuit includes carbon adsorption, desorption, and regeneration, primary water treatment, and a tailings impoundment facility. A gravity concentration circuit, while optional, captured an average of 32% of the recovered gold production at the historical Omai operation. A gravity circuit at a new Omai plant would also improve process performance by recovering coarse gold and reduce the risk of gold accumulation elsewhere in the circuit. Gravity recoverable gold, greater than 25 microns, recovered from secondary cyclone underflow would be subjected to separate intensive leaching on a much smaller mass, which would have the effect of slightly decreased retention time requirements in the main carbon-in-leach circuit. An SABC configuration provides flexibility for possible staged development and/or future expansion. Initially, the Semi-Autogenous Grinding mill can operate as an SSAC circuit (single-stage Semi-Autogenous Grinding and pebble crusher) to achieve the target grind size. The grinding circuit can later be expanded by adding a secondary ball mill which would increase installed power and support higher throughput at the same target grind size. Future expansions of an Omai processing plant could benefit from Guyana's potential near-future development of lower cost, green energy solutions. The Amaila Falls 165mW hydropower project, located 110 miles west of Omai, has recently been out for tender, with the design including a transmission line to within 22 km of the proposed Omai plant site. Another potential future alternative power source is the planned Liquified Natural Gas plant near the capital city of Georgetown, located about 165 km by paved highway from the Omai turnoff.
