Osisko Development Files Technical Report on Mineral Resource Estimate for the Trixie Deposit, Tintic Project

Press Release

Montreal, Québec,  – Osisko Development Corp. (NYSE: ODV, TSXV: ODV) (“Osisko Development” or the “Company”) announces the filing of a technical report (the “Technical Report”) for the updated mineral resource estimate (“MRE”) on its 100%-owned underground Trixie deposit (the “2024 Trixie MRE”), within the Company’s wider Tintic Project (“Tintic” or the “Tintic Project”), located in the historic East Tintic Mining District in central Utah, U.S.A. Highlights from the previously-announced 2024 Trixie MRE disclosed in the Company’s news release dated March 15, 2024 are presented below, and are consistent with the Technical Report.

The Technical Report, titled “NI 43-101 Technical Report, Mineral Resource Estimate for the Trixie Deposit, Tintic Project, Utah, United States of America” and dated April 25, 2024 (with an effective date of March 14, 2024), was prepared for the Company by independent representatives of Micon International Limited in accordance with National Instrument 43-101 – Standards of Disclosure for Mineral Projects (“NI 43-101”). Reference should be made to the full text of the Technical Report, which is available electronically on SEDAR+ (www.sedarplus.ca) and on EDGAR (www.sec.gov) under Osisko Development’s issuer profile and on the Company’s website at https://osiskodev.com/tintic-project.

2024 TRIXIE MINERAL RESOURCE ESTIMATE

Table 1: 2024 Trixie MRE (all zones) – March 14, 2024

				Tonnes			Au Grade			Contained			Ag Grade			Contained
	Classification									Gold						Silver
				(000’s)			(g/t)						(g/t)
										(000’s oz)						(000’s oz)
	Measured		120			27.36			105			61.73			238
	Indicated		125			11.17			45			59.89			240
	Measured and Indicated			245			19.11			150			60.80			478
	Inferred		202			7.80			51			48.55			315

Notes (applicable to Tables 1, 2, and 3)

1. Effective date of the 2024 Trixie MRE is March 14, 2024.
2. Each of Mr. William Lewis, P.Geo., of Micon International Limited and Alan J. San Martin, MAusIMM(CP), of Micon International Limited (i) has reviewed and validated the 2024 Trixie MRE, (ii) is considered to be independent of the Company for purposes of Section 1.5 of National Instrument 43-101 – Standards of Disclosure for Mineral Projects (“NI 43-101”), and (iii) is a “qualified person” within the meaning of NI 43-101.
3. The mineral resources were estimated using the Canadian Institute of Mining (“CIM”), Metallurgy and Petroleum’s “CIM Definition Standards on Mineral Resources and Mineral Reserves” adopted by the CIM council.
4. Mineral resources are reported when they are within potentially mineable shapes derived from a stope optimizer algorithm, assuming an underground longhole stoping mining method with stopes of 6.1 m x 6.1 m x minimum 1.5 m dimensions.
5. Mineral resources that are not mineral reserves do not have demonstrated economic viability.
6. Geologic modelling was completed by Osisko Development modeling geologist Jody Laing, P.Geo, using Leapfrog Geo software. The 2024 Trixie MRE was completed by Osisko Development chief resource geologist, Daniel Downton, P.Geo using Datamine Studio RM 2.0 software. William Lewis and Alan J. San Martin of Micon International Limited independently reviewed and validated the mineral resource model.
7. The estimate is reported for an underground mining scenario and with USD assumptions. The cut-off grade of 4.32 g/t Au was calculated using a gold price of US$1,750/oz, a CAD:USD exchange rate of 1.30; total mining, processing and G&A costs of US$168.04/imperial ton; a refining cost of US$2.65/ounce; a combined royalty of 4.50%; and an average metallurgical gold recovery of 80%.
8. The stope optimizer algorithm evaluated the resources based on a gold equivalent grade which incorporates the silver grade estimate and assumes a silver price of US$23/oz and metallurgical silver recovery of 45%.
9. The 2024 Trixie MRE is comprised of six zones within the greater Trixie area: T2, T3, T4, Wild Cat, 40 Fault and 75-85.
10. Average bulk density values in the mineralized domains were assigned to the T2 (2.955 T/m³), T3 (2.638 T/m³), T4(2.618 T/m³), Wild Cat, and 40 Fault (2.621 T/m³), and 75-85 (2.617 T/m³) domains.
11. Inverse Distance Squared interpolation method was used with a parent block size of 1.2 m x 2.4 m x 2.4 m.
12. The 2024 Trixie MRE results are presented in-situ. Calculations used metric units (metres, tonnes, g/t). The number of tonnes is rounded to the nearest thousand. Any discrepancies in the totals are due to rounding effects.
13. Neither the Company nor Micon International Limited is aware of any known environmental, permitting, legal, title-related, taxation, socio-political, marketing or other relevant issue that could materially affect the mineral resource estimate other than disclosed in this news release.
14. Technical information in this news release differs from similar information made public by U.S. companies subject to the reporting and disclosure requirements of the U.S. Securities and Exchange Commission. See below under “Cautionary Statement to U.S. Investors”.

Table 2: 2024 Trixie MRE Separated by Domain – March 14, 2024

	Domain			Category			Tonnes			Grade			Contained			Grade			Contained
										(Au g/t)			Gold (oz)			(Ag g/t)			Silver (oz)
				Measured		22,678			106.27			77,484			115.99			84,572
	T2			Indicated		11,939			23.19			8,902			51.07			19,602
				M+I			34,617			77.62			86,387			93.60			104,173
				Inferred		1,996			9.82			630			61.38			3,938
				Measured		2,385			9.46			725			75.34			5,776
	T3			Indicated		970			5.47			171			57.32			1,787
				M+I			3,355			8.30			896			70.13			7,564
				Inferred		139			6.27			28			63.14			282
	T4 +			Measured		94,784			8.93			27,227			48.41			147,520
				Indicated		51,827			6.48			10,795			37.59			62,637
	Wild
	Cat +			M+I			146,611			8.07			38,023			44.58			210,156
	40 FLT
				Inferred		104,676			6.57			22,127			38.57			129,792
				Measured		–						–						–
75-85				Indicated		60,008			12.93			24,943			80.95			156,185
				M+I			60,008			12.93			24,943			80.95			156,185
				Inferred		94,793			9.12			27,784			59.28			180,666
				Measured			119,847			27.36			105,437			61.73			237,868
	Total			Indicated			124,743			11.17			44,811			59.89			240,211
				M+I			244,590			19.11			150,248			60.80			478,078
				Inferred			201,603			7.80			50,569			48.55			314,678

Refer to notes described under Table 1, which are also applicable to Table 2 in their entirety.

Table 3: Trixie MRE Cut-Off Grade (“COG”) Sensitivity (Base Case in Bold) – March 14, 2024

	Classification			Tonnes			COG			Grade			Contained			Grade			Contained
										(Au g/t)			Gold (oz)			(Ag g/t)			Silver (oz)
			366,130			2.50			13.79			162,348			50.18			590,666
			324,251			3.00			15.23			158,722			53.31			555,740
			291,005			3.50			16.64			155,716			56.19			525,681
			261,219			4.00			18.14			152,350			58.95			495,091
	Measured +			244,590			4.32			19.11			150,248			60.80			478,078
	Indicated		237,143			4.50			19.58			149,266			61.52			469,058
			217,327			5.00			20.99			146,677			64.07			447,646
			198,538			5.50			22.55			143,909			66.19			422,504
			182,842			6.00			24.01			141,164			68.57			403,074
			165,955			6.50			25.81			137,734			71.39			380,902

 

	152,986	7.00	27.55	135,503		74.34	365,663
	438,189	2.50	5.26	74,056		34.46	485,528
	342,880	3.00	5.99	66,034		38.38	423,112
	279,722	3.50	6.65	59,767		41.84	376,306
	224,039	4.00	7.42	53,438		46.31	333,578
	201,603	4.32	7.80	50,569		48.55	314,678
Inferred	190,002	4.50	8.02	49,009		49.90	304,803
	163,894	5.00	8.60	45,313		53.08	279,718
	141,728	5.50	9.16	41,742		55.92	254,818
	123,472	6.00	9.71	38,532		58.70	233,028
	106,080	6.50	10.35	35,291		60.43	206,087
	91,725	7.00	10.99	32,397		61.91	182,579

Note: Micon International Limited’s “qualified person” (for purposes of NI 43-101) has reviewed the COG used in the sensitivity analysis relating to the 2024 Trixie MRE and is of the opinion that the individual cut-off grades used in the sensitivity analysis meet the test of reasonable prospects of economic extraction. The numbers in bold represent the current 2024 Trixie MRE.

Table 4: Trixie MRE Cut-off Grade Calculation Breakdown

PARAMETERS	VALUES
Mining Cost ($/ST)	$74.33
G&A ($/ST)	$52.71
Heap Leach ($/ST)	$41.00
Total Refining Cost/ OZ	$2.65
Gold Price	$1,750
Royalty (Combination)	4.50%
Heap Leach Au Recovery	80.0%
Cut-off Grade (COG)	4.32

Qualified Persons

The scientific and technical information contained in this news release has been reviewed and approved by Maggie Layman, P.Geo., Vice President, Exploration of Osisko Development, and a “qualified person” within the meaning of NI 43-101 (“QP”).

The independent QPs for the 2024 Trixie MRE, within the meaning of NI 43-101, are William Lewis, P.Geo. and Alan J. San Martin MAusIMM(CP) of Micon International Limited. Each QP is independent of Osisko Development within the meaning of NI 43-101 and has reviewed and approved the content in this news release.

Quality Assurance (QA) – Quality Control (QC)

All drill core and exploration samples are dispatched to ALS Geochemistry or SGS Canada for offsite sample preparation and analysis. Both labs are ISO/IEC 17025 certified, and ALS Geochemistry is also ISO 9001 certified. Samples are assigned a unique sample ID. All geological and sampling information is entered into a Datamine Fusion database. Core is sawn in half and half is sampled. Certified standards and blanks are inserted into all sample dispatches. Samples are collected by Old Dominion Transportation and dispatched to SGS Canada’s laboratory in Burnaby, British Columbia or ALS Geochemistry’s laboratories in Elko, Nevada or Twin Falls, Idaho. Sample submission forms accompany the samples, and digital copies are emailed to the destination lab.

Core sample preparation is completed by ALS Geochemistry or SGS Canada, including drying, crushing, and pulverizing of samples. Analytical assays include gold by 30-gram fire assay with AAS finish, and gold overlimits by fire assay with gravimetric finish. Screen metallic analyses are performed on selected samples. Multielement analysis (including silver) is by four-acid digest with ICP-AES/ICP-MS finish. The pulps are returned to Osisko Development and coarse rejects are disposed after 90 days. Assays are reported to Osisko Development and then loaded into Datamine Fusion. Quality Assurance-Quality Control samples are checked, and assays are merged with sample information for future reporting.

Underground face samples are collected by Company geologists from each of the active mining faces, with samples transported by the geologists from Trixie to the on-site Company laboratory located at the Burgin administrative complex. Underground samples are dried, crushed to <10 mm and a 250 g split is taken. The split is pulverized, and a 30 g Fire Assay with gravimetric finish is completed to determine gold and silver grades, reported in oz/short ton and g/t.

The Company’s Burgin laboratory is not a certified analytical laboratory, but the facility is managed by a qualified laboratory manager with annual auditing by technical staff. The laboratory has been independently audited by Qualitica Consulting and Micon International Limited’s QP with recommendations implemented. Inter-laboratory check assays using ALS Geochemistry as a third-party independent analysis of samples is routinely carried out as part of ongoing QA/QC work. Certified OREAS QC standards and blanks are inserted at regular intervals in the sample stream to monitor laboratory performance.

True width is estimated to be approximately 0.5 m – 3 m (1.6 – 10 ft) for all fissure veins and discrete structures (T2, T3, 75-85, Wildcat and 40 Fault) and the T4 zone is modelled at an average width of 90 m (300 ft) and encompasses disseminated mineralization and discontinuous veins ranging from several cm to 1 m (3 ft).

ABOUT OSISKO DEVELOPMENT CORP.

Osisko Development Corp. is a North American gold development company focused on past-producing mining camps located in mining friendly jurisdictions with district scale potential. The Company’s objective is to become an intermediate gold producer by advancing its 100%-owned Cariboo Gold Project, located in central B.C., Canada, the Tintic Project in the historic East Tintic mining district in Utah, U.S.A., and the San Antonio Gold Project in Sonora, Mexico. In addition to considerable brownfield exploration potential of these properties, that benefit from significant historical mining data, existing infrastructure and access to skilled labour, the Company’s project pipeline is complemented by other prospective exploration properties. The Company’s strategy is to develop attractive, long-life, socially and environmentally sustainable mining assets, while minimizing exposure to development risk and growing mineral resources.

For further information, visit our website at www.osiskodev.com or contact:

Sean Roosen		Philip Rabenok
Chairman and CEO		Director, Investor Relations
Email: sroosen@osiskodev.com		Email: prabenok@osiskodev.com
Tel: +1 (514) 940-0685		Tel: +1 (437) 423-3644

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