Columbus Gold Corporation announced the results of comprehensive metallurgical test work from Columbus Gold's 100% controlled Montagne d'Or Gold Deposit, Paul Isnard Project, in French Guiana. Three gold recovery process options were investigated on master composites: 1) whole-ore cyanidation, 2) a combination of gravity concentration followed by cyanidation of gravity tailing, and 3) gravity concentration followed by gold flotation from the gravity tailing. The metallurgical tests were performed on two master composites prepared from 3.3 tonnes of whole core intervals from the UFZ and the LFZ.

Triplicate fire assays for gold and silver showed that the UFZ master composite averaged 1.50 g/t Au and 3.33 g/t Ag and the LFZ composite averaged 1.56 g/t Au and 4.67 g/t Ag. The response of test samples to different process methods are summarized as follows: Baseline leaching of ground whole ore for 72-hours in 0.5g/L sodium cyanide extracted 94.7% of the gold from the UFZ master composite and 97.0% of the gold from the LFZ master composite ore at a grind size of 80% passing (P80) 75µm. Gravity separation was able to recover up to 47.9% of the gold from the UFZ master composite and 40.2% of the gold from the LFZ master composite into gravity cleaner concentrates representing about 0.1 wt.% of the test material. Overall gold recoveries from the test flowsheet, which included gravity concentration followed by cyanidation of the gravity tailing, were slightly better than the recoveries achieved from whole-ore cyanidation at the same P80 75µm grind size.

Gravity concentration followed by rougher flotation of the gravity tailings at a grind size of P80 75µm achieved 96.8% gold recovery from the UFZ master composite and 96.6% gold recovery from the LFZ master composite. This included 20.6-47.9% of the gold reporting to gravity concentrate and 48.8-72.8% of the gold reporting to the flotation rougher concentrate. Combined silver recovery into combined gravity and flotation concentrates ranged from 80-89%.

Metallic screen assays indicate the presence of coarse gold in the Montagne d'Or test composites. The 30-50% gravity recoverable gold obtained from the gravity process also confirms this finding.