Mr. Robert Wares reports

OSISKO METALS REPORTS PRELIMINARY METALLURGICAL TESTWORK RESULTS FROM GASPE COPPER

Osisko Metals Inc. has released preliminary metallurgical and grindability test work results from the Gaspe copper project located near Murdochville in the Gaspe peninsula in Quebec. Test work was performed on 18 composite samples of mineralized drill core from selected intersections of the 2023 drill program at Copper Mountain, and employed a conventional copper-molybdenum (Cu-Mo) flotation flowsheet and reagents.

Highlights:

• Copper recoveries averaged 91.9 per cent from 19 bulk Cu-Mo locked-cycle flotation tests (including one composite sample) and averaged 94.2 per cent from three locked-cycle Cu-Mo separation tests.
• Copper concentrate grades averaged 24.1 per cent Cu from 19 bulk Cu-Mo locked-cycle flotation tests and averaged 28 per cent Cu from three locked-cycle Cu-Mo separation tests.
• Molybdenum recoveries averaged 84.3 per cent and concentrate grades averaged 1.18 per cent Mo from 19 locked-cycle Cu-Mo bulk tests. Molybdenum recoveries averaged 72.3 per cent and concentrate grades averaged 0.85 per cent Mo from three bulk Cu-Mo locked-cycle Cu-Mo separation test. Molybdenum stage recoveries average 87.2 per cent and concentrate grade averaged 58.8 per cent Mo. The overall combined molybdenum recoveries averaged 65.2 per cent.
• Silver (Ag) recoveries averaged 71.1 per cent from 19 bulk Cu-Mo locked-cycle flotation tests and averaged 71.8 per cent from the three locked-cycle Cu-Mo separation tests, with concentrate grades averaging 120 grams per tonne (g/t) Ag for all locked-cycle tests.
• Eighteen grindability tests produced an average bond rod mill work index (RWi) of 13.8 kWh/t (kilowatt-hours per tonne) and an average bond ball mill work index (BWi) of 10.5 kWh/t, indicating average hardness of mineralized material.

Robert Wares, chief executive officer and chairman of the board, commented: "Preliminary test work on Copper Mountain material has produced excellent numbers. At approximately 92 per cent average copper recoveries and 65 per cent molybdenum recoveries, these results indicate that Gaspe copper should produce both copper and molybdenum concentrates with excellent metal grades and a payable silver credit added to the copper concentrate. These results have surpassed expectations relative to historical numbers from past production at Copper Mountain and will provide positive input into ongoing PEA work. Pending multielement analyses of final concentrates will provide trace element data that will establish if any smelter penalty thresholds are reached, and this additional information will be disclosed as soon as possible. Work on the updated mineral resource estimate (MRE) for Copper Mountain is also progressing well and we expect to release the new MRE in the coming weeks."

Metallurgical test work

A bench-scale metallurgical test work program was undertaken at Base Metallurgical Laboratories located in Kamloops, B.C. The test work program included:

1. Sample characterization;
2. Grindability;
3. Conventional flotation flowsheet and reagent schemes;
4. Batch and locked-cycle Cu-Mo bulk flotation tests to produce copper and molybdenum concentrates;
5. Composite Cu-Mo bulk flotation followed by Cu-Mo separation tests;
6. Head grades tested ranged from 0.21 per cent to 0.90 per cent copper, 44 grams per tonne (g/t) to 1,347 g/t molybdenum and 0.9 g/t to five g/t silver.

Sample selection

Eighteen composite samples, totalling 1,100 kilograms (kg), produced from drill core providing a suitable range of copper grades were selected for metallurgical testing. Head assays for the 18 composite samples ranged from 0.21 per cent to 0.90 per cent copper, 44 g/t to 1,347 g/t molybdenum, 0.9 g/t to five g/t silver and 0.01 g/t to 0.07 g/t gold. The table entitled "Details of metallurgical sample selection" provides drill hole intervals and composite head grades for the metallurgical samples.

Testing procedures

Composites were created based on the selected drill core intervals (see the table "Bulk Cu-Mo LCT [lithium-cesium-tantalum] results"). Once created, each composite was stage crushed to nominal 1.5-inch (3.8-centimetre (cm)) representative mass was split out for SMC testing at the minus 31.5 mm and plus 26.5 mm range. Once SMC testing was completed, the products were returned and the composites were again stage crushed to minus one-half inch (minus 1.3 cm) where 15 kg was removed for rod mill work index testing. The remaining mass was stage-crushed to minus six mesh. The crushed material was blended and split into 24 kg sublots, each sublot was rotary split into two kg charges. A single test charge was riffle split to remove 250 g for head assay. The head cuts were pulverized to 80 per cent passing 75 micrometres.

Metallurgical samples comprising drill core were crushed, split and subsampled for comminution test work and head assays. Samples were wet-grinded in a closed batch mill at 65 per cent solids targeting the required grind size. Ground samples were discharged into a flotation cell and pulp-level adjusted to the appropriate volume and density for flotation testing. The pulp was conditioned with reagents before beginning flotation. A series of open-circuit batch rougher and cleaner flotation tests were undertaken to optimize flotation conditions prior to operating locked-cycle flotation tests. The combined rougher concentrate was dewatered ahead of regrinding while retaining the process water for the cleaner stage. The rougher concentrate was reground to a target size with the regrind discharge size confirmed by laser particle sizing. The reground product was cleaned in successive dilution stages. The final concentrate and intermediate tails were filtered and dried separately in a low-temperature oven before assaying.

The general approach to locked cycle testing was conducted as per the batch tests. Each cycle test was completed with five cycles, the rougher and first cleaner were completed open circuit, the intermediate cleaner tailings were recirculated to the feed of each subsequent stage for the following cycle; that is, the third cleaner tailing of cycle A was recirculated to the second cleaner feed of cycle B, the second cleaner tail A was recirculated to the feed of the first cleaner feed B. This process continued for cycles C, D and E. All final products and final intermediate streams were filtered, dried and assayed for metallurgical balancing. Locked cycle testing provides a methodology to best estimate steady-state metallurgical projections for a full-scale operation.

Reagents used for bulk Cu-Mo flotation included lime, potassium amyl xanthate (PAX), 3418A and methyl isobutyl carbinol (MIBC). Nitrogen sparging, fuel oil, sodium hydrosulfide (NaHS) and MIBC were used for Cu-Mo separation.

Analysis was completed on pulverized sample splits using wet digestion methods for copper, molybdenum and silver. In each case, the samples were digested by a strong oxidization using a combination of aqua regia, potassium chlorate and bromine. Copper was analyzed using atomic adsorption (AA) spectroscopy, and molybdenum and silver by inductively coupled plasma optical emission spectroscopy (ICP-OES).

Metallurgical tests assay quality is evaluated by producing material balances of all products reconciled head which is compared with the direct head for all elements in consideration.

Grindability

Grindability tests were performed on each of the metallurgical samples. The average SMC Axb value was 46.6, average bond ball mill work index was 10.49 kWh/t, average rod mill work index (RWi) was 13.89 kWh/t and average abrasion index (Ai) was 0.384.

Batch flotation tests

A composite sample was initially tested with average copper grade to determine the optimal grind size for further flotation tests. Four grind sizes ranging from 80 per cent passing (P80) of 66 microns to 125 microns were tested. P80 of 75 microns was selected as the primary grind size for further testing.

Bulk Cu-Mo locked cycle flotation

Cu-Mo locked cycle tests (LCT) were performed at a grind size of 75 microns for the rougher stage with regrind to a target of 30 microns for the cleaner stages. The table entitled "Bulk Cu-Mo LCT results" shows the bulk Cu-Mo concentrate grades and recovery results. Copper concentrate grades ranged from 17.1 per cent to 30.9 per cent with recoveries ranging from 86.1 per cent to 95.7 per cent. Molybdenum grades ranged from 0.08 per cent to 2.74 per cent with recoveries ranging from 75.7 per cent to 92.3 per cent.

Cu-Mo separation

To produce molybdenum concentrates, due to the low feed concentrations, metallurgical samples were combined to produce three larger composite samples (low-, medium- and high-grade copper samples) for batch bulk flotation tests and subsequent Cu-Mo separation testing. The table entitled "Composite sample assays for Cu-Mo separation tests" shows the composite sample head grades. Copper head grades ranged from 0.26 per cent to 0.55 per cent, molybdenum grades ranged from 135 g/t to 234 g/t and silver head were consistently 2.2 g/t.

Multiple large batch flotation tests were performed for each composite sample to produce bulk Cu-Mo concentrates followed by Cu-Mo separation tests. Three Cu-Mo separation locked cycle tests were performed at a grind size of 30 microns for the rougher stage with regrind to a target of 15 microns for the cleaner stages. The table entitled "Copper concentrate assays and recoveries" shows final copper concentrate grades and recoveries for the locked cycle tests. Copper grade ranged from 22.2 per cent to 30.9 per cent with recoveries ranging from 92.3 per cent to 96.6 per cent.

The table entitled "Molybdenum concentrate assays and recoveries" shows final molybdenum concentrate grades and recoveries for the locked cycle tests. Molybdenum grade ranged from 55.7 per cent to 60.7 per cent with recoveries ranging from 57.7 per cent to 70.7 per cent.

Full multielement analyses of final concentrates are pending, and further testing is planned during 2024 to further optimize metallurgical performance.

Qualified person

Christian Laroche is a consultant for Synectiq Inc. and the independent qualified person (QP) responsible for the technical data related to all testing reported in this press release. Mr. Laroche is a registered member of the Ordre des Ingenieurs du Quebec.

About Osisko Metals Inc.

Osisko Metals is a Canadian exploration and development company creating value in the critical metals space, more specifically copper and zinc. The company is a joint venture partner with Appian Capital Advisory LLP for the advancement of one of Canada's premier past-producing zinc mining camps, the Pine Point project, located in the Northwest Territories, for which the 2022 PEA (as defined herein) has indicated an after-tax net present value (NPV) of $602-million and an internal rate of return (IRR) of 25 per cent, based on long-term zinc price of $1.37 (U.S.)/pound (lb) and the current mineral resource estimates that are amenable to open-pit and shallow underground mining. The current mineral resource estimate in the 2022 PEA consists of 15.7 million tonnes (Mt) grading 5.55 per cent zinc equivalent (ZnEq) of indicated mineral resources and 47.2 Mt grading 5.94 per cent ZnEq of inferred mineral resources. Please refer to the technical report entitled "Preliminary economic assessment, Pine Point project, Hay River, Northwest Territories, Canada," dated Aug. 26, 2022 (with an effective date of July 30, 2022), which was prepared for Osisko Metals and PPML by representatives of BBA Engineering Inc., HydroRessources Inc., PLR Resources Inc. and WSP Canada Inc. Please refer to the full text of the 2022 PEA, a copy of which is available on SEDAR+ under the Osisko Metals' issuer profile, for the assumptions, methodologies, qualifications and limitations described therein. The Pine Point project is located on the south shore of Great Slave Lake in the Northwest Territories, near infrastructure, with paved highway access, an electrical substation, as well as 100 kilometres of viable haulage roads.

In addition, the company also acquired, in July, 2023, from Glencore Canada Corp., a 100-per-cent interest in the past-producing Gaspe copper mine, located near Murdochville in the Gaspe peninsula of Quebec. The company is currently focused on resource evaluation of the Mount copper deposit that hosts (in accordance with National Instrument 43-101 -- Standards of Disclosure for Mineral Projects) an inferred mineral resource of 456 Mt grading 0.31 per cent Cu (see April 28, 2022, news release of Osisko Metals entitled "Osisko Metals announces maiden resource at Gaspe copper -- inferred resource of 456 Mt grading 0.31 per cent copper"). Gaspe Copper hosts the largest undeveloped copper resource in eastern North America, strategically located near existing infrastructure in the mining-friendly province of Quebec.

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