Vancouver, B.C. - January 8, 2020- Otis Gold Corp. (“Otis” or the “Company”) (TSX-V: OOO) (OTC: OGLDF) is pleased to announce up to 92.6% gold recovery from column leach metallurgical testing of near-surface mineralized volcanic rock at its Kilgore Project. The test samples came from drill hole 17OKC-379, a larger diameter PQ drill hole that contained a true width interval of 120 feet (35.6 metres) with a calculated head grade of 1.49 g/t Au; the PQ core hole was a twin of 17OKC-356.
•Gold extraction of 92.6% on half-inch (0.5”) crush columns over 200 days (see Figure 1).
•Gold extraction of 85.9% on one and a half-inch (1.5”) crush columns over 200 days.
•Gold extraction of 56.1% on three-inch (3.0”) crush columns. The three-inch column was terminated after 120 days once no further gold extraction was recorded.
•Finer crush sizes improved the gold extraction rate, reaching 60% gold extraction in approximately 24 days (0.5”) versus 56 days at the next coarser crush size (1.5”).
•Notable was that at 0.5” and 1.5” crush sizes gold recoveries had not plateaued after 200 days.
•Gold recoveries for 0.5” crush and simulated 3.0” Run-of-Mine (ROM) mineralized material processing are significantly higher than the respective 82% and 50% recoveries used in the Kilgore Preliminary Economic Assessment (see Otis News Release dated August 27, 2019).
•Silver was also recovered during all phases of testing. Column leach extractions were 41.9%, 37.2% and 17.4% respectively (see Table 1), indicating that additional work is required to assess silver’s potential impact on Kilgore’s economics.
Table 1: Summary of Column Leach Results
Size Extraction % Residue Assay Calc. Head NaCN
Au Ag Au
0.5" 92.6 41.9 0.111 1.3 1.493 2.2 4.664 4.561
1.5" 85.9 37.2 0.143 1.8 1.012 1.8 3.260 1.276
3.0" 56.1 17.4 0.313 2.1 0.713 2.5 2.362 1.121
Otis submitted approximately 450kg of PQ core from drill hole 17OKC-379 to Resource Development Inc. of Denver, CO for metallurgical testing. The drill samples to be tested came from the interval: 13ft (4.0m) to 133ft (40.5m), an interval of 120ft (35.6m), and returned head assays of 1.49 g/t Au and 2.2 g/t Ag, including 5ft (1.52m) from 119ft to 124ft (36.3-37.8m) of 42.68 g/t Au and 15 g/t Ag. These assays are significantly higher than those from the original, smaller diameter, HQ core hole 17OKC-356 which returned a mineralized interval of 124ft (37.8m) averaging 0.31 g/t Au; the difference in returned gold values highlighting the variable nature of gold mineralization at Kilgore. The samples, as analyzed in both holes, came from near surface, hydrothermally altered and oxidized rhyolite-composition lithic tuffs.
Metallurgical testing of the samples consisted of:
•Initial head grade assay of each of the drill intervals submitted
•Bench-top bottle roll leach tests
•Column leach tests at 0.5-inch, 1.5-inch and 3.0-inch crush sizes
The test work was conducted to confirm the suitability of this material to treatment by cyanide heap leaching and to validate the crush size required for efficient gold extraction. Each of the tests was conducted in a typical heap leach configuration. Mineralogical examination of the higher-grade gold occurrences within the samples submitted revealed gold grains associated with Jarosite, a mineral product of oxidation of iron sulfides, varying in size from <2 microns to 70 microns (Figure 2).
see More on