Mr. John Burzynski reports
OSISKO REPORTS INCREASED GOLD RECOVERY RESULTS AT MARBAN
Osisko Mining Inc. has released results of 135 oxygenated bottle-roll gold leaching tests and 16 crushing/grinding tests on core samples representing the mineralized zones of the Marban and Norlartic deposits, located on its 100-per-cent-owned Marban property near the town of Malartic, Que.
The Marban and Norlartic deposits have combined in-pit resources estimated at 37 million tonnes at 1.24 g/t (grams per tonne) gold for 1.48 million ounces in the measured and indicated categories, and 3.6 million tonnes at 1.15 g/t gold for 134,000 ounces in the inferred category. These resources are estimated from two optimized Whittle pit shells at a cut-off grade of 0.4 g/t gold and using a gold price of $1,250 (U.S.) per ounce (see press release dated June 13, 2016).
Highlights:
- Average gold recovery of 91.1 per cent for the Marban deposit (increase of 2.8 per cent
from previous results);
-
Average gold recovery of 93.2 per cent for the Norlartic deposit;
-
The Bond ball mill grindability tests (work index) gave an average of
11.6 kilowatt-hours per tonne for the Marban deposit and of 12.6 kilowatt-hours per tonne for the Norlartic
deposit.
Bottle-roll leaching tests
A total of 135 samples (100 from the Marban deposit and 35 from Norlartic) were ground to an average grain size of 65 microns, oxygenated (preaerated) for one hour and leached for 36 hours.
For the Marban deposit, the results indicate an average recovery of 91.1 per cent over a grade range of 0.24 to 4.37 g/t gold (average grade of 1.42 g/t gold) with average cyanide (NaCN) consumption of 0.07 kilogram per tonne. The samples were separated in five populations, and the results are summarized in the attached table. Recoveries were improved due to preaeration of samples with respect to testing done in 2015. For the Norlartic deposit, the samples were separated in four populations and gave an average recovery of 93.2 per cent on a grade interval of 0.39 to 3.11 g/t gold with an average grade of 1.49 g/t gold. The average NaCN consumption is 0.05 kilogram per tonne. The results are summarized in the attached table.
RESULTS OF THE 100 BOTTLE-ROLL LEACHING TESTS ON THE MARBAN DEPOSIT
Number of Grade range Average grade Average P NaCN consumption Recovery Recovery
Samples (g/t Au) (g/t Au) 80 (um) (kg/t) range (%)
(%)
12 0.24 to 0.50 0.37 61 0.07 79.1 to 95.8 89.6
32 0.51 to 1.00 0.74 65 0.06 72.9 to 97.7 93.1
19 1.01 to 1.50 1.26 64 0.07 83.6 to 97.1 92.7
25 1.51 to 2.50 2.04 64 0.08 68.0 to 97.8 88.1
12 2.51 to 4.37 3.24 65 0.07 67.6 to 97.9 91.0
Average 0.24 to 4.37 1.42 64 0.07 - 91.1
Median - 1.17 64 0.06 - 93.4
RESULTS OF THE 35 BOTTLE-ROLL LEACHING TESTS ON THE NORLARTIC DEPOSIT
Number of Grade range Average grade Average P NaCN consumption Recovery Recovery
Samples (g/t Au) (g/t Au) 80 (um) (kg/t) range (%)
(%)
Nine 0.39 to 1.00 0.63 66 0.04 89.6 to 96.8 93.5
Nine 1.01 to 1.50 1.25 65 0.04 92.3 to 95.1 93.2
Eight 1.51 to 2.00 1.71 65 0.05 90.2 to 94.1 92.6
Nine 2.01 to 3.11 2.39 63 0.05 91.9 to 95.6 93.4
Average 0.39 to 3.11 1.49 65 0.05 - 93.2
Median - 1.45 64 0.04 - 93.1
Six samples from the Marban deposit gave recovery results below 80 per cent, which are likely due to the presence of coarse gold grains. These samples are found in four of the five populations. Nevertheless, as previously established (see NioGold's July 6, 2015, press release), the grade/recovery curve is near horizontal, signifying that the recovery does not decrease with lower grades. The Norlartic deposit samples show a much more homogeneous recovery, and similarly to Marban, show a flat grade/recovery curve. These gold cyanide leach test results are comparable with those obtained at the Canadian Malartic mine, located about 15 kilometres from the Marban project, for similar operating conditions used until 2015.
Comminution tests
A total of 16 samples (10 from the Marban deposit and six from the Norlartic deposit) composed of PQ-calibre core (diameter of 85 millimetres) were submitted for JK drop-weight tests, Bond low-energy impact tests and Bond rod mill/Bond ball mill grindability tests.
The results at different grind sizes are categorized as medium to very
hard for the coarse-sized fraction (CWI), moderately soft to moderately
hard for the medium-sized fraction (RWI) and soft to medium for the fine-sized fraction (BWI). The Bond ball mill grindability tests (work index)
gave an average of 11.6 kilowatt-hours per tonne for the Marban deposit and of 12.6 kilowatt-hours per tonne
for the Norlartic deposit.
The results of the grindability tests demonstrate that the rock quality would not be problematic for an SABC circuit type commonly used in open-pit operations such as the Canadian Malartic mine.
RESULTS OF THE 10 COMMINUTION TESTS ON THE MARBAN DEPOSIT
JK parameters Work index (kwh/t)
Statistics Relative A x b ta (1) SCSE CWI RWI BWI
density (kWh/t)
Average 2.80 40.8 0.63 10.39 14.8 14.3 11.6
Standard deviation 0.03 17.6 0.20 1.28 3.75 2.00 1.38
Relative standard
deviation 1.00 43 31 12 25 14 12
Minimum (1) 2.75 89.5 1.13 7.23 11.3 10.3 9.4
10th percentile 2.77 46.5 0.73 9.53 11.5 12.4 10.2
25th percentile 2.78 39.4 0.67 10.11 11.8 12.7 10.5
Median 2.80 35.7 0.61 10.66 14.4 15.4 11.6
75th percentile 2.81 33.8 0.54 10.91 16.1 15.6 12.9
80th percentile 2.81 32.8 0.51 11.07 16.7 15.6 13.1
90th percentile 2.81 30.3 0.45 11.57 18.4 15.9 13.1
Maximum (1) 2.85 28.6 0.44 11.94 23.3 16.5 13.5
(1) Minimum and maximum refer to the softest and hardest results, respectively.
RESULTS OF THE SIX COMMINUTION TESTS ON THE NORLARTIC DEPOSIT
JK parameters Work index (kwh/t)
Statistics Relative A x b ta (1) SCSE CWI RWI BWI
density (kWh/t)
Average 2.75 34.7 0.36 10.93 15.5 13.9 12.6
Standard deviation 0.03 8.8 0.12 1.33 1.99 1.73 1.75
Relative standard
deviation 1.00 25 32 12 13 12 14
Minimum (1) 2.72 48.3 0.55 9.21 13.7 12.0 10.4
10th percentile 2.73 44.3 0.50 9.60 13.8 12.3 10.9
25th percentile 2.74 39.1 0.42 10.12 14.1 12.5 11.4
Median 2.76 33.9 0.32 10.80 14.8 13.6 12.6
75th percentile 2.78 28.9 0.27 11.65 16.4 15.1 13.9
80th percentile 2.78 27.8 0.26 11.84 16.9 15.3 14.0
90th percentile 2.78 25.8 0.26 12.38 17.9 15.8 14.4
Maximum (1) 2.78 23.8 0.26 12.92 18.8 16.2 14.7
(1) Minimum and maximum refer to the softest and hardest results, respectively.
Quality control and qualified persons
The metallurgical testing program is designed and supervised by Christian Laroche, Ing, and Yan Ducharme, MSc, PGeo, who are qualified persons as defined by the National Instrument 43-101. The metallurgical testing and the analyses were performed by SGS Mineral Services of Lakefield, Ont. This news release was written, reviewed and approved by Mr. Laroche and Mr. Ducharme.
About the Marban project
The Marban project is located in the Malartic mining camp in the Abitibi gold district of Quebec. The current in situ mineral resource estimate on the Marban, Norlartic and Kierens deposits is 38.2 million tonnes at a grade of 1.29 g/t gold for 1.59 million ounces in the measured and indicated categories, and 4.1 million tonnes at a grade of 1.47 g/t gold for 195,000 ounces in the inferred category. The Marban project contains three past-producing mines (Marban, Norlartic and Kierens), which collectively produced 585,000 ounces of gold between 1959 and 1992. The land package owned by Osisko in the heart of the Cadillac, Malartic and Val d'Or gold mining camps covers 125 square kilometres, and these camps currently host six producing gold mines, including the Canadian Malartic mine located near the Marban project.
About Osisko Mining Inc.
Osisko holds a 100-per-cent interest in the high-grade Windfall Lake gold deposit located between Val d'Or and Chibougamau in Quebec. It also holds a 100-per-cent undivided interest in a large area of claims in the surrounding Urban Barry area (82,400 hectares), a 100-per-cent interest in the Marban project located in the heart of Quebec's prolific Abitibi gold mining district, and properties in the Larder Lake mining division in Northeast Ontario, including the Jonpol and Garrcon deposits on the Garrison property, the Buffonta past-producing mine, and the Gold Pike mine property. Osisko also holds interests and options in a number of additional properties in Northern Ontario.
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