Metallurgical Information

Metallurgical testwork has been completed using oxide and sulphide mineralized samples from Tepal North Zone (NZ), Tepal South Zone (SZ) and the Tizate Zone.

Initial metallurgical testing was undertaken on samples from the two Tepal zones (NZ and SZ) in 1973 by INCO Ltd and Teck-Cominco Corporation. The INCO testwork mainly focused on developing a sulphide flotation circuit to produce a copper concentrate, while the Teck testwork program was directed on cyanide leaching of oxide mineralization to recover gold.

Further metallurgical tests were performed between 2009 and 2013, using representative oxide and sulphide samples by G&T Metallurgical Services, Limited (G&T) of Kamloops, British Columbia, (now ALS Metallurgy) and at McClelland Laboratories, Inc. (MLI) of Sparks, Nevada.

The scope of the testwork completed to date on oxide mineralization includes column and bottle roll cyanide leach tests, gravity separation, flotation and acid leaching to recover acid soluble copper. Sulphide testwork has mainly focused on flotation to recover a copper concentrate with precious metal credits, with cyanide leaching of scavenged pyrite. A variability program has also been completed to test flotation performance against comminution variability throughout the deposit.

The flowsheet selected for the sulphide mineralization from all three zones comprises a conventional grinding and flotation circuit to produce a copper concentrate containing acceptable copper grades (>23% Cu) and payable gold and silver values. Cyanide leaching to recover additional precious metals from the cleaner tailings and scavenged pyrite concentrate from the copper rougher tailings is also proposed for inclusion into the overall sulphide process flowsheet.

Flotation locked cycle tests (LCT) have been undertaken using composite samples from all sulphide mineralized zones. These tests suggest copper and gold recoveries into a 23% Cu concentrate of 86% and 54% for the North/South Zones and 84% and 50% for the Tizate Zone mineralization.

The concentrates produced contained no significant quantities of deleterious elements.

Sequential pyrite rougher flotation of the copper rougher tailings determined that an additional 20% of the silver and 30% of the gold can be recovered into a combined copper cleaner tailings and pyrite concentrate. Cyanide leaching extracted about 75% of the silver and 70% of this gold from this combined stream.

Multiple comminution tests showed an average Bond Ball Work Index for sulphide mineralization of 14.4 kWh/t with an 80 percentile of 16.1 kWh/t based on 42 samples tested. The average Drop Weight Index was 7.4 kWh/m³ with 80 percentiles of 9.0 kWh/m³. JKTech rated the samples to be moderately hard to very hard.

There is potential to recover gold from the oxidized mineralization by using cyanide heap leaching or agitation leaching. Encouraging results were achieved for all the mineralized zones tested.