Metallurgical Test Work
Metallurgical test work was completed by SGS on samples from both the Marathon and Leprechaun deposits. The test program included chemical head analysis, comminution, metallurgical (gold recovery) and tailing detoxification testing. Test work focused on examining the potential for gold extraction, primarily by applying a grind, gravity separation, flotation, concentrate regrind and cyanide leaching of both the reground flotation concentrate and the flotation tailing flowsheet. More work was completed on a fine grind, gravity separation and gravity tailing leach option. The potential for gold recovery from relatively low-grade samples was also examined.
Ore characterization included chemical head analysis on material from five sub zones representing each of the Marathon and Leprechaun deposits. The same sub zones were subjected to comminution testing, including bond rod mill work index (RWi), ball mill work index (BWi) and abrasion index (Ai) tests. QEMSCAN-RMS analysis was conducted on equally weighted composites of both deposits to determine mineralogy.
The average Marathon deposit sample gold grade tested was 3.23 g/t compared to 3.41 g/t for Leprechaun. Grades varied from ~2.0 to ~4.1 g/t Au for Marathon and from ~2.6 to ~5.2 g/t Au in the Leprechaun sub-composites.
Gold recovery test work extensively examined numerous typical parameters within the three primary unit operations; gravity separation, flotation and cyanide leaching. The Marathon and Leprechaun deposit composites showed similar gold recoveries/extractions in excess 96%. The average recoverability of the low-grade (head grade<1.0 g/t Au) composites was essentially the same (>96%) as the higher-grade material (head grade ~3.3 g/t Au).