Cariboo Gold’s 2M oz Mine Plan and the 3.6M oz Sitting Behind It

Osisko Gold Group’s mine plan for the Cariboo gold project rests on 2 million ounces in reserve. Yet the company already holds access to another 3.6 million ounces through infrastructure it is building anyway. That gap between what is planned and what is reachable is where the investment case actually lives.

The formal construction decision landed on 14 September 2026, and the clock is now running. As of 31 July 2026, the project sits at roughly 22% complete, and Osisko has assembled approximately US$1.7 billion in available funds against a go-forward capital requirement of about C$990 million.

This is the moment the pieces line up: the construction schedule is defined, the financing is in place, and the resource optionality is finally visible to anyone watching. What follows here is a clear read on what Cariboo looks like as a construction asset today, what the resource expansion thesis actually depends on, and what the Proserpine discovery adds to the district. The question to hold throughout is whether the distance between the current mine plan and the wider resource inventory is priced in, or whether it is sitting in plain sight.

Where Cariboo stands: construction milestones and the 2029 production clock

Walk onto the Cariboo site today and you find a project past the drawing-board stage. Detailed engineering is roughly 40% complete, procurement is around 44% finished, and Osisko has committed approximately C$325 million to long-lead items, the equipment with the longest delivery times that tends to dictate a construction schedule.

The overall figure worth anchoring on is this.

Overall project completion (as of 31 July 2026): approximately 22%

Much of that progress predates the formal decision. Osisko staged early works deliberately, and the results are physical: the waste dump facility is around 80% complete, mill site excavation is also near 80%, the primary water treatment facility is operational, and roughly 3 km of underground development has been driven from the Cow Portal into the Lowhee and Cow zones.

Pre-FID works: what was already built before the formal decision

That early-works staging matters because it compresses the effective construction timeline. By the time the board formally approved full development, the company had already completed supporting facilities and pushed underground access forward. The formal decision did not start the physical build; it confirmed a build that was already underway, which is a meaningfully lower-risk position than approving a project from a standing start.

From here, the schedule is precise. JDS is the primary construction contractor, and the plan runs 30 months to first gold and 36 months to commercial production from 1 August 2026. The milestone sequence looks like this:

1. Construction start: 1 August 2026
2. Major earthworks ramp-up through Q4 2027
3. Process plant foundations: summer 2027
4. Plant building enclosure: Q2 2028
5. First gold pour: Q1 2029
6. Commercial production: H2 2029

The current workforce sits at around 550, heading toward a peak of roughly 613-615 direct jobs.

Here is what the completion figures tell you as an investor. At 22% overall and 40% engineering, with major procurement locked, the project has cleared the phase where delays come from planning gaps. The risk has shifted to execution: earthworks pace, contractor throughput, and underground development rates. Every milestone hit compresses the distance between capital committed and cash generated, and Q1 2029 is the anchor against which financing costs and resource conversion must now be measured.

The financing stack: what US$1.7 billion in available funds actually means

Construction certainty means little without the money to see it through, and this is where Cariboo’s story sharpens. On 23 September 2026, Osisko priced US$600 million of senior secured notes carrying a 9.250% coupon, maturing 1 October 2031, issued at 100.0% of par.

The detail that signals credibility is the sizing. The offering was launched at US$500 million and upsized to US$600 million before pricing, on the back of investor demand. When bond buyers ask for more paper than the issuer initially planned to sell, they are expressing confidence in the project’s ability to service the debt.

The proceeds are structured with discipline. Roughly US$120.9 million repays and terminates the Appian project facility, a portion funds a segregated interest reserve account covering the first five semi-annual coupon payments (beginning 1 April 2027), and the balance goes into a ring-fenced disbursement account earmarked for construction.

The notes are guaranteed by Barkerville Gold Mines Ltd. and key subsidiaries, secured by first-priority liens on project assets.

The Cariboo capital stack has evolved considerably over the past 12 months, with the Appian facility retirement and the upsized senior secured notes representing a meaningful shift in creditor seniority and covenant structure that shapes how future cost overruns would be absorbed.

Total available funds: approximately US$1.7 billion, against go-forward capital of roughly C$990 million. Osisko characterises itself as fully financed with surplus.

Here is what the structure tells you. The upsizing combined with an interest reserve covering nearly three years of coupons means Osisko has built headroom to absorb a meaningful cost overrun before the capital structure strains. For a development-stage gold project, financing certainty is the single most decisive variable, and the segregated disbursement account plus the pre-funded interest reserve removes much of the refinancing risk that typically shadows projects of this scale during construction.

Beyond the mine plan: what 3.6 million accessible ounces and 16 drill rigs tell you

The financing pays for a mine built around 2 million ounces at 4,900 tonnes per day. But the resource geometry is where the longer thesis takes shape, and the numbers are worth slowing down for.

Alongside that 2-million-ounce reserve sits an additional 3.6 million measured, indicated, and inferred ounces, all accessible through the mine infrastructure already being built. As part of the development, roughly 30 km of underground tunnels are under construction, and that same tunnel network reaches ounces well beyond the initial plan. The priority during construction is converting a minimum of 2 million of those 3.6 million accessible ounces into reserve status.

The infrastructure cost is already sunk into the first 2 million ounces, which means each additional ounce converted to reserve carries a materially lower incremental capital burden, and resource-to-reserve conversion at this scale depends on drill density, metallurgical test work, and economic cut-off assumptions that can shift materially as the resource model matures.

The depth extension opportunity and what the vertical metre math implies

The scale question comes into focus at depth. Current resources are defined to just 350 metres, yet drilling has already tested mineralisation to 1,100 metres, with a target extension to 1,500 metres, roughly five times the current resource floor. Drilling has confirmed the mineralised system continues below the classified zones.

The figure that makes this material is the yield estimate.

Estimated average yield: approximately 15,000 ounces per vertical metre.

Apply that math across an extended depth profile and the potential production picture widens considerably. Osisko estimates annual production potential of 200,000 to 400,000 ounces if mining chambers are doubled per development kilometre. The important caveat: the deeper zones are not yet classified as reserves, so this remains a drilling story rather than a booked resource.

To test it, the company is drilling hard. The key program metrics:

• Active drill rigs: 16 (three underground)
• Target: 30 rigs within 6-12 months
• Drilling budget: US$160 million over 24 months
• Conversion priority: at least 2 million of the 3.6 million accessible ounces to reserve status

For an investor, the implication is specific. The infrastructure cost is already sunk into the first 2 million ounces, which means each additional ounce converted to reserve carries a materially lower incremental capital burden than the first ounce did. The US$160 million drilling commitment signals that management sees a deposit geometry capable of supporting a substantially larger operation than the current mine plan implies.

Proserpine: why a 7 km open-pit target changes the district picture

Cariboo’s optionality does not end at depth. Around 7 km southeast along strike sits Proserpine, a target that behaves like a genuinely separate thesis rather than an extension of the main deposit.

Start with what the drill actually returned. Initial drilling of 6,463 metres across 14 surface holes (February to May 2026, results released 5 August 2026) expanded the mineralised footprint to roughly 1.0 km along strike by 0.5 km wide, open in all directions, within a larger 6.0 km by 1.0 km gold-in-soil anomaly. Every hole that reached target depth hit mineralisation.

The headline intercept anchors the grade story.

95.93 g/t Au over 4.60 m at approximately 71 m depth, including 873.00 g/t Au over 0.50 m.

Supporting results included 5.46 g/t Au over 8.60 m at around 77 m and 2.17 g/t Au over 14.45 m at roughly 431 m, with mineralisation confirmed from near surface past 400 m depth.

The structural contrast with the main deposit is what makes Proserpine strategically distinct. It sits at higher elevation, above the regional groundwater table, which makes it a candidate for open-pit mining. Cariboo, by contrast, sits at the base of a valley next to a lake and a river, where open-pit permitting was undesirable and an underground design was the sensible route.

That above-water-table position is not a geological footnote. In British Columbia’s water-focused regulatory environment, a shallower pit with well-understood hydrology can carry simpler dewatering, more straightforward water-treatment design, and a potentially cleaner permitting pathway. For an investor weighing project risk, that could make a Proserpine open pit a lower-risk capital allocation than a second underground build.

The regional context stretches the picture further. The mineralised trend runs 86 km, of which only 4.4 km, roughly 6%, has been drill-tested. Proserpine is the first material satellite to emerge from the untested remainder, with 26,500 metres of follow-up drilling planned and three rigs active. If a comparable mine were built there, Osisko points to 400,000 ounces from known mineralisation, with stated upside at depth.

The takeaway for the reader: Proserpine raises the prospect of a second standalone operation sharing processing and infrastructure with Cariboo, a scenario reflected in neither the 2-million-ounce mine plan nor any public resource estimate for the satellite.

Investors wanting to stress-test the open-pit scenario in more detail will find our deep-dive into the Proserpine discovery covers the full drill hole database, grade continuity analysis, and the structural geology that distinguishes Proserpine from the main Cariboo deposit.

Assessing Cariboo as an investment: what the data supports and where the gaps remain

Set the constructive case and the risk case side by side, and the picture is neither uncritical optimism nor reflexive doubt. Both sides are real.

The constructive case rests on four pillars:

• Financing certainty: roughly US$1.7 billion available against C$990 million go-forward capital
• Construction momentum: 22% complete with major procurement locked and early works largely done
• Resource optionality: 3.6 million accessible ounces plus the Proserpine target
• A supportive gold price environment that enabled the upsized US$600 million bond

Key risks to monitor as construction advances

The risks are equally concrete:

• Schedule execution: the 30-month timeline demands tight coordination between earthworks, civil construction, and underground development. Any critical-path slip could push first gold beyond Q1 2029 and compress early cash flow against the 9.250% coupon.
• Resource conversion: the 3.6 million accessible ounces include inferred material that may not all convert at assumed cut-off grades, recoveries, and costs. No new NI 43-101 estimate for the main deposit appeared in 2026 filings reviewed, so the conversion thesis remains a drilling story.
• Cost escalation: actual capex could exceed C$990 million if contingencies prove thin in a remote British Columbia setting. No public credit rating from S&P, Moody’s, or Fitch has been disclosed for the notes.
• Environmental and community factors: water quality obligations, tailings management, and Indigenous community engagement remain ongoing considerations.

This article is for informational purposes only and should not be considered financial advice. Investors should conduct their own research and consult with financial professionals before making investment decisions.

The calibration question is direct. Does the gap between 2 million reserve ounces and roughly 5.6 million total accessible ounces represent genuine optionality trading at a discount, or conversion risk the current price does not yet reflect? These are not obscure risks; they are the standard risks of large-scale remote mining construction. That means an investor’s edge comes from tracking the specific signals, earthworks pace, underground development rates, and drilling conversion results, that will decide which case is closer to right.

What Cariboo’s full resource picture means for the district’s long-term production potential

Zoom out from the single asset and the district thesis comes into view.

The regional trend runs 86 km, of which only 4.4 km, roughly 6%, has been drill-tested.

Proserpine is the first material satellite to emerge from the untested 94%, and the exploration program aimed at the broader corridor is referred to internally as “Rolling Thunder 2.” If the depth extension thesis delivers at 15,000 ounces per vertical metre from 350 m toward 1,500 m, and Proserpine’s open-pit potential firms up around 400,000 ounces with upside at depth, the district could support a production profile well beyond what the current 4,900 tpd plan implies. That remains conditional on drilling results, not a booked outcome.

For investors assessing the broader regional context, our full explainer on British Columbia’s critical minerals sector covers the provincial policy framework, infrastructure investment trends, and the competitive dynamics shaping which projects attract capital in the current cycle.

Past performance does not guarantee future results, and these production scenarios are speculative and subject to change based on drilling outcomes and market conditions.

For investors, the most informative catalysts over the next 12-18 months are not construction completion, which is still years out. They are the resource and exploration signals, in roughly this order:

1. Drilling conversion results from the 16-to-30 rig ramp, and a future NI 43-101 update for the main deposit
2. Proserpine’s follow-up 26,500 m program results
3. Earthworks progress through Q4 2027 as the first major construction test

The read to take from this is straightforward. First gold arrives in Q1 2029, with commercial production in H2 2029, but the market’s long-term production assumptions will be revised well before then. Investors who track the Proserpine drilling and the conversion results from the rig ramp will get earlier signal on whether the district thesis is materialising than those watching construction updates alone.