Osisko Development

Highlights

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Location
British Columbia, Canada

Ownership
100%

Mine Type
Underground

Land Package
~192,000 hectares

Metals
Gold, Silver

Project Status
Shovel ready (permits granted Q4 24)

Overview

A Feasibility Study on the Cariboo Gold Project, released in April 2025, envisions a robust and scalable underground operation expected to produce approximately 1.89 million ounces of gold over a 10-year mine life, with an after-tax NPV5% of C$943 million and 22.1% IRR at a US$2,400/oz gold price (after-tax NPV5% of C$2,066 million and 38.0% IRR at a US$3,300/oz gold price). The Project received an Environmental Assessment Certificate on October 10, 2023, in accordance with the BC Environmental Assessment Act (2018). Receipt of the EA Certificate successfully concluded the EA process for the Project, which was launched in October 2019. The Company was granted the BC Mines Act and Environmental Management Act permits in Q4 2024.

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Optimized Feasibility Study (2025)

Feasibility Study

April 2025

The scientific and technical information related to the 2025 Feasibility Study ("2025 FS") relating to the Cariboo Gold Project is supported by the 2025 FS which was prepared in accordance with NI 43-101 with an effective date of April 22, 2025 and will be filed on SEDAR+ (www.sedarplus.ca) and on EDGAR (www.sec.gov) under Osisko Development's issuer profile within 45 days of the date of April 28, 2025. For readers to fully understand the information in this news release, reference should be made to the full text of the Technical Report, once filed, including all assumptions, qualifications and limitations therein. The Technical Report is intended to be read as a whole, and sections should not be read or relied upon out of context. Refer to ODV news release dated April 28, 2024. The 2025 FS has been prepared by independent representatives of BBA, InnovExplo, a subsidiary of Norda Stelo, Alius, Falkirk, WSP, Okane, Integrated Sustainability, Clean Energy, and JDS, each of whom is a "qualified person" (within the meaning of NI 43-101) (each, a "QP").

Table 1: Cariboo Feasibility Study Highlights

Cariboo Gold 2025 FS vs. 2023 FS – Project Operating and Financial Metrics
Assumptions	units	2023 FS	2025 FS
Gold price	US$/oz	1,700	2,400
Exchange rate	USDCAD	1.30	1.35
Discount rate	%	5.0%	5.0%
Production
Mine life	yrs	12.0	10.0
Total ore mined	kt	16,703	17,815
Peak annual throughput	tpd	4,900	4,900
Average gold head grade	g/t Au	3.78	3.62
Total contained gold	koz	2,031	2,071
Avg. gold recovery	%	92.0%	92.6%
Total recovered gold, payable	koz	1,869	1,894
Avg. gold production, LOM	koz/yr	164	190
Avg. gold production, first 5 yrs	koz/yr	96	202
Operating Unit Costs
Underground mining	$/t mined	53.6	62.3
Processing	$/t mined	31.2	23.2
Water and waste management	$/t mined	7.2	5.0
Electrical transmission line	$/t mined	—	4.9
General and administrative	$/t mined	10.7	15.4
Total unit operating costs	$/t mined	102.6	110.7
Total operating costs	$ mm	1,714	1,921
Royalty payments	$ mm	206	292
Offsite charges	$ mm	5	143
Operating Costs
Total cash costs²	US$/oz	$792	$947
AISC²	US$/oz	$968	$1,157
Capital Expenditures
Initial costs	$ mm	137.3	881
Expansion costs	$ mm	451.1	—
Sustaining costs	$ mm	466.6	426
Closure costs, net³	$ mm	(38.9)	99
Total capex	$ mm	1,016	1,406
Economics (after-tax)
Total free cash flow, LOM²	$ mm	901	1,577
Net Present Value (NPV5%)	$ mm	502	943
Internal Rate of Return (IRR)	%	20.7%	22.1%
Payback, from commercial production	yrs	5.9	2.8
Average free cash flow, first 5 yrs²	$ mm	(63)	296
Average free cash flow, LOM²	$ mm	75	158

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View Notes [+]

Total may not add up due to rounding.
Cash costs, all-in sustaining costs per ounce and free cash flow are non-IFRS measures or ratios. Refer to "Non-IFRS Financial Measures" at the end of this news release for more information. Total cash costs are presented on a per ounce payable basis inclusive of total operating costs mining costs, processing costs, site G&A costs, royalties, smelting, refining, and transports costs. AISC are presented on a per ounce payable basis and include cash costs plus sustaining and closure costs.
Closure costs are shown net of salvage value.
Pre-final investment decision capital costs total $38.6 million.

Table 2: Economic Sensitivities to Gold Price (base case in bold)

Cariboo Gold 2025 FS – Economic Sensitivity Analysis, after-tax (base case in bold)
Gold Price	NPV5%	IRR	Payback	Avg. FCF
(US$/oz)	($ mm)	(%)	(yrs)	($ mm per yr)
$1,800	251	9.9%	5.3	65
$2,100	610	16.5%	3.5	113
$2,400	943	22.1%	2.8	158
$2,700	1,275	27.2%	2.2	204
$3,000	1,604	31.9%	1.9	250
$3,300	1,934	36.3%	1.7	296
$3,600	2,263	40.5%	1.5	342
$3,900	2,592	44.5%	1.3	388
$4,200	2,921	48.3%	1.2	433
$4,500	3,249	51.9%	1.1	479

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Mineral Reserves & Resources

Mineral Resources Estimate (April 22, 2025) – Exclusive of Mineral Reserves

The Mineral Resources estimate included in the 2025 FS have an effective date of April 22, 2025, and are reported exclusive of Mineral Reserves. Mineral Resources that are not Mineral Reserves do not have demonstrated economic viability. There is no certainty that Mineral Resources will be converted into Mineral Reserves. Mineral Resources include Inferred Mineral Resources which have had insufficient work to classify them as Indicated Mineral Resources. It is uncertain but reasonably expected that Inferred Mineral Resources could be upgraded to Indicated Mineral Resources with continued exploration. The Mineral Resources estimate follows the 2014 CIM Definition Standards on Mineral Resources and Reserves and the 2019 CIM Estimation of Mineral Resources and Mineral Reserves Best Practice Guidelines.

Mineral Resources	Measured Resources			Indicated Resources			Inferred Resources
Deposit	Tonnes (000’s)	Grade (g/t Au)	Ounces (koz Au)	Tonnes (000’s)	Grade (g/t Au)	Ounces (koz Au)	Tonnes (000’s)	Grade (g/t Au)	Ounces (koz Au)
Bonanza Ledge	47	5.06	8	32	4.02	4	—	—	—
BC Vein	—	—	—	1,057	3.00	102	596	3.17	61
KL	—	—	—	527	2.80	47	2,514	2.53	205
Lowhee	—	—	—	1,333	2.76	118	486	3.01	47
Mosquito	—	—	—	1,553	2.96	148	1,883	3.08	186
Shaft	—	—	—	6,121	2.92	575	7,457	3.44	826
Valley	—	—	—	2,718	2.70	236	2,470	3.01	239
Cow	—	—	—	3,991	2.91	374	3,368	2.78	301
Total Resources	47	5.06	8	17,332	2.88	1,604	18,774	3.09	1,864

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View Notes [+]

The independent and qualified persons for the Mineral Resources estimates, as defined by NI 43-101, are Carl Pelletier, P.Geo., and Tessa Scott, P.Geo. (Norda Stelo). The effective date of the 2025 Feasibility Study Mineral Resource Estimate is April 22, 2025.
These Mineral Resources, exclusive of the reserves, are not Mineral Reserves and do not have demonstrated economic viability.
The Mineral Resources estimate follows the 2014 CIM Definition Standards on Mineral Resources and Reserves and the 2019 CIM Estimation of Mineral Resources and Mineral Reserves Best Practice Guidelines.
A total of 481 vein zones were modelled for the Cow Mountain (Cow and Valley), Island Mountain (Shaft and Mosquito), Barkerville Mountain (BC Vein, KL, and Lowhee) deposits and one gold zone for Bonanza Ledge. A minimum true thickness of 2.0 m was applied, using the gold grade of the adjacent material when assayed or a value of zero when not assayed.
The estimate is reported for a potential underground scenario at a cut-off grade of 1.8 g/t Au, except for Bonanza Ledge at a cut-off grade of 3.5 g/t Au. The cut-off grade for the Cow, Valley, Shaft, Mosquito, BC Vein, KL, and Lowhee deposits was calculated using a gold price of US$2,400/oz; a USDCAD exchange rate of 1.35; an underground mining cost of $66.3/t; a processing and transport cost of $30.80/t; a G&A plus Environmental cost of $22.40/t; and a sustaining CAPEX cost of $45.6/t. No changes have been applied for the Bonanza Ledge. The cut-off grade for the Bonanza Ledge deposit was calculated using a gold price of US$1,700/oz; a USDCAD exchange rate of 1.27; an underground mining cost of $79.13/t; a processing and transport cost of $65.00/t; and a G&A plus Environmental cost of $51.65/t. The cut-off grades may be re-evaluated in light of future prevailing market conditions (metal prices, exchange rate, mining cost, etc.).
Density values for Cow, Shaft, Lowhee, and BC Vein were estimated using the ID2 interpolation method, with a value applied for the non-estimated blocks of 2.80 g/cm³ for Cow, 2.78 g/cm³ for Shaft, 2.74 g/cm³ for Lowhee, and 2.69 g/cm³ for BC Vein. Median densities were applied for Valley (2.81 g/cm³), Mosquito (2.79 g/cm³), and KL (2.81 g/cm³). A density of 3.20 g/cm³ was applied for Bonanza Ledge.
A four-step capping procedure was applied to composited data for Cow (3.0 m), Valley (1.5 m), Shaft (2.0 m), Mosquito (2.5 m), BC Vein (2.0 m), KL (1.75 m), and Lowhee (1.5 m). Restricted search ellipsoids ranged from 7 to 50 g/t Au at four different distances ranging from 25 m to 250 m for each deposit. High grades at Bonanza Ledge were capped at 70 g/t Au on 2.0 m composited data.
The gold Mineral Resources for the Cow, Valley, Shaft, Mosquito, BC Vein, KL, and Lowhee vein zones were estimated using Datamine StudioTM RM 1.9 software using hard boundaries on composited assays. The dilution halo gold mineralization was estimated using Datamine StudioTM RM Pro 1.11. The OK method was used to interpolate a sub-blocked model (parent block size = 5 m x 5 m x 5 m). Mineral Resources for Bonanza Ledge were estimated using GEOVIA GEMSTM 6.7 software using hard boundaries on composited assays. The OK method was used to interpolate a block model (block size = 2 m x 2 m x 5 m).
Results are presented in situ. Ounce (troy) = metric tons x grade / 31.10348. Calculations used metric units (metres, tonnes, g/t). The number of tonnes were rounded to the nearest thousand. Any discrepancies in the totals are due to rounding effects. Rounding followed the recommendations as per NI 43-101.
The qualified persons responsible for this section of the technical report are not aware of any environmental, permitting, legal, title, taxation, socio-economic, marketing, political, or other relevant factors that could materially affect the Mineral Resource estimate other than those disclosed in this news release and in the Technical Report.

Mineral Reserves Estimate (April 10, 2025)

Mineral Reserves were classified in compliance with the CIM Definition Standards for Mineral Resources and Mineral Reserves. As such, the Mineral Reserves are based on Measured and Indicated Mineral Resources and do not include any Inferred Mineral Resources. Measured and Indicated Mineral Resources are exclusive of proven and probable reserves. Mineral Reserves are the estimated tonnage and grade of ore that is considered economically viable for extraction.

Mineral Reserves for the Project deposit incorporate dilution and mining recovery factors based on the selected mining method and design. In addition, economic analyses were completed to validate the profitability of particular areas of the reserves.

Cariboo Gold 2025 FS – Mineral Reserves Statement (April 10, 2025)
Category / Zone	Tonnage	Gold Grade	Contained Gold
	(tonnes)	(g/t)	(oz)
Proven	—	—	—
Probable
Cow	3,999,971	3.35	430,548
Valley	3,238,636	3.59	374,058
Shaft	8,548,295	3.72	1,021,599
Mosquito	1,105,370	3.94	140,102
Lowhee	923,162	3.52	104,491
Total Proven & Probable	17,815,435	3.62	2,070,798

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View Notes [+]

Totals may not add up due to rounding.
The Mineral Reserve estimate follows the 2014 CIM Definition Standards on Mineral Resources and Reserves and the 2019 CIM Estimation of Mineral Resources and Mineral Reserves Best Practice Guidelines.
Mineral Reserves used the following assumptions: US$1,915/oz gold price, USD:CAD exchange rate of 1.32, and variable cut-off value from 1.70 g/t to 2.0 g/t Au
Mineral Reserves include both internal and external dilution along with mining recovery. The external dilution is estimated to be 10.1%. The average mining recovery factor was set at 91.3% to account for ore left in each block in the margins of the deposit.