Sentinel Metals Hits 48m at 1.13g/t Gold in Stacked Zones; Resource Update Coming
Key Takeaways
- DDCO26-003 intersected multiple stacked gold zones from just 18.0m depth, returning a headline intercept of 48m @ 1.13g/t Au including a high-grade core of 6.1m @ 3.50g/t Au and a peak of 1.5m @ 12.1g/t Au, with 100% core recovery through the high-grade zone.
- Fire assay results for maiden hole DDCO26-001 confirm the previously reported PhotonAssay grade of 5.5g/t Au, reconciling within 3–6% across the key 46.8m @ 5.33g/t Au interval — validating the headline result with the industry-standard method ahead of the November MRE update.
- Three of the first four holes at Columbia have now returned gold in the shallow part of the system, with DDCO26-004 hitting gold from the very first sample at 12.0m depth.
- The deep test DDCO26-002 (700.8m, the deepest hole ever at Columbia) returned no significant gold, but the stratigraphic data has been incorporated into the geological model underpinning the November 2026 Mineral Resource Estimate update.
- Columbia currently hosts an Inferred Resource of 21.4Mt @ 1.3g/t Au for 920,000oz of gold (JORC 2012), with the updated MRE targeted for November 2026 incorporating all 2026 drilling data.
Columbia drilling delivers multiple stacked gold zones in latest results
Sentinel Metals (ASX: SNM) has reported fire assay results for diamond holes DDCO26-002, -003 and -004 from its maiden drilling program at the 100%-owned Columbia Gold-Silver Project in Montana, USA. The results add to a growing body of evidence that the Columbia system hosts substantial mineralisation beyond its current resource footprint.
The standout result is DDCO26-003, which intersected multiple stacked gold zones over approximately 140m downhole from 18.0m, returning a headline intercept of 48m @ 1.13g/t Au. Fire assays have also confirmed the exceptional maiden hole result for DDCO26-001, originally reported via PhotonAssay on 10 August 2026.
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Q1 FY27 drilling highlights at a glance
- DDCO26-003: 48m @ 1.13g/t Au from 18.0m, including 6.1m @ 3.50g/t Au and a high-grade spike of 1.5m @ 12.1g/t Au; 100% core recovery through the high-grade zone
- DDCO26-004: Gold returned from the very first sample — 7.0m @ 0.82g/t Au from 12.0m and 5.7m @ 1.34g/t Au from 45.0m
- DDCO26-001 (fire assay confirmation): 46.8m @ 5.33g/t Au from 88.2m (PhotonAssay: 5.5g/t Au); reconciles within 3–6% of the PhotonAssay result; high-grade sub-interval of 13.5m @ 15.7g/t Au
- DDCO26-002: No significant gold returned (peak 0.19g/t Au); deepest hole drilled at Columbia to date at 700.8m; structural and stratigraphic data incorporated into the geological model
Matt Herbert, Managing Director
“Our maiden drilling program at Columbia continues to deliver exciting results, reinforcing the significant mineral endowment of the Columbia mineral system and highlighting strong growth potential beyond the current Mineral Resource and known mineralisation.
“Importantly, DDCO26-003 intersected three stacked gold zones starting from near-surface, including a high-grade core assaying up to 12g/t and, importantly, 100% core recovery through that zone. The hole returned an impressive wide intercept of 48m @ 1.13g/t Au. In addition, DDCO26-004 returned gold from the first sample. That means three of our first four holes hit gold in the shallow part of the system, with most of the program assays still to come.
“DDCO26-002 was our first deep test. While it did not intersect significant mineralisation, it has given us our first look beneath the deposit with this information going straight into our geological model. The rig continues drilling high-priority holes, with the next batch of assays due in October, and the updated Mineral Resource Estimate on track for release in November.”
Breaking down the results hole by hole
DDCO26-003 — stacked zones and high-grade core
DDCO26-003 was drilled from pad F to a depth of 171.1m, targeting the central part of the deposit to validate historical drilling and extend mineralisation into an open area. The hole encountered gold from 18.0m depth and intersected multiple stacked mineralised zones to 159.5m.
The headline intercept of 48m @ 1.13g/t Au from 18.0m includes three constituent zones:
- 17.8m @ 1.00g/t Au from 39.1m, including 3.0m @ 3.28g/t Au
- 17.5m @ 0.82g/t Au from 60.5m
- 6.1m @ 3.50g/t Au from 81.0m, including 1.5m @ 12.1g/t Au
Core recovery averaged 94% across the entire hole, with 100% recovery through the high-grade zone at 81.0–87.1m. For resource estimation purposes, that level of recovery in a high-grade interval is a meaningful data quality positive — it means the grade is based on representative, uncompromised sample material.
Deeper intercepts of 2.5m @ 2.59g/t Au from 123.0m and 2.5m @ 1.64g/t Au from 157.0m confirm that mineralisation persists below the oxide zone into fresh sulphide material, a detail that matters for the scope of any future resource update.
DDCO26-004 — gold from the first sample
DDCO26-004 was drilled from pad Q to 100.0m, testing the continuity of the Rover vein in a poorly drilled area of the deposit. The headline is straightforward: gold was returned from the very first sample at 12.0m depth.
Key intercepts from the hole include:
- 7.0m @ 0.82g/t Au from 12.0m
- 5.7m @ 1.34g/t Au from 45.0m, including 2.6m @ 2.55g/t Au
- 10.1m @ 0.42g/t Au from 74.0m
Core recovery through the shallow oxide zone was lower, recorded at 51% through the 12.0–19.0m intercept and 79% through the 45.0–50.7m intercept. This is characteristic of near-surface oxide ground, where chemically weathered material is more prone to core loss, and the company has reported these figures transparently alongside each intercept in Table 1.
DDCO26-002 — deep test adds geological intelligence
DDCO26-002 was the deepest hole ever drilled at Columbia, reaching 700.8m from pad B. Its target was the deep conductive anomaly identified by the 2025 HSAMT survey beneath the deposit. No significant gold was returned, with a peak assay of just 0.19g/t Au.
The hole intersected approximately 440m of andesitic volcanics before entering a sedimentary sequence at 458.9m downhole, with silicified calcareous mudstone from 577.0m to end-of-hole. Alteration is described as weak and lacking the assemblages that host gold elsewhere at Columbia. While the result is negative from a gold perspective, the geological data acquired represent the deepest stratigraphic information obtained at Columbia to date, and it has been incorporated into the geological model supporting the November 2026 MRE update. A deep test that eliminates a geophysical target still adds value by narrowing the search space and focusing future drilling on higher-priority zones.
What is an epithermal gold system — and why does Columbia’s style matter?
Epithermal gold-silver systems are deposits formed at relatively shallow crustal depths by hot, mineralising hydrothermal fluids. Gold and silver are carried by these fluids and precipitate in fractures and breccias, typically producing steeply dipping vein-hosted gold zones. Columbia is classified as a low- to intermediate-sulphidation epithermal system, hosted in Eocene volcanic rocks.
The “stacked zones” seen in DDCO26-003 are a structurally positive feature. Multiple mineralised veins intersected at varying depths within a single drill hole increase the overall volume of mineralised material that can potentially be captured in a resource estimate, rather than relying on a single thick intercept.
The distinction between the oxide zone (near-surface, chemically weathered material) and fresh sulphide material (at depth, below the redox boundary) is also relevant here. Both can be gold-bearing, and the confirmation in DDCO26-003 that gold mineralisation persists below the oxide boundary into fresh sulphide material at depth is a meaningful signal for resource growth potential.
Fire assays confirm maiden hole result — why this reconciliation matters
Fire assay results for DDCO26-001 confirm the PhotonAssay grades reported on 10 August 2026, with the two independent methods reconciling within 3–6% across the high-grade zones. The table below compares the two methods across the key intervals from Table 3 of the source announcement.
| Zone | From–To (m) | Interval (m) | PhotonAssay Au (g/t) | Fire Assay Au (g/t) | Difference |
|---|---|---|---|---|---|
| Oxide | 34.5–52.0 | 17.6 | 0.8 | — | — |
| Oxide | 72.0–83.5 | 11.5 | 0.9 | 0.77 | -4% |
| Oxide – high-grade zone | 88.2–135.0 | 46.8 | 5.5 | 5.33 | -3% |
| incl. high-grade sub-interval | 105.5–119.0 | 13.5 | 16.6 | 15.7 | -6% |
| incl. bracketing interval (upper) | 88.2–105.5 | 17.3 | 1.1 | 1.23 | +12% |
| incl. bracketing interval (lower) | 119.0–135.0 | 16.0 | 1.0 | 1.02 | +2% |
| Fresh | 142.9–160.0 | 17.1 | 0.4 | 0.38 | -5% |
| Fresh | 170.0–178.2 | 8.2 | 0.7 | 0.64 | -9% |
| Fresh | 183.5–198.0 | 14.5 | 0.8 | 0.71 | -11% |
| Fresh – deepest | 215.5–218.0 | 2.5 | 0.9 | 0.85 | -5% |
| Peak sample | 110.77–114.00 | 3.23 | 40.7 | 41.3 | +1% |
Fire assay is considered the industry-standard method for gold determination. The close reconciliation between the two independent methods strengthens confidence in the grade reported for DDCO26-001. The fire assay data will be used for DDCO26-001 in the November 2026 MRE update.
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What comes next — resource update and final assay batches
The program is approaching its conclusion, with a clear sequence of catalysts ahead:
- Drilling scheduled to conclude in early October 2026 ahead of winter
- Assays for DDCO26-005 to DDCO26-007 expected in October 2026
- Further assay batches to follow as the program concludes
- An updated Columbia Mineral Resource Estimate is targeted for November 2026, incorporating all 2026 drilling data including fire assay data for DDCO26-001
- Follow-up drilling of the deeper HSAMT conductor and breccia target is planned; 2027 program planning is underway
Columbia currently hosts an Inferred Mineral Resource of 21.4Mt @ 1.3g/t Au for 920,000oz of gold (JORC 2012). The November MRE update will reflect all new drilling data collected across the deposit during the 2026 program.
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