Sentinel’s Columbia drilling sets up a bigger November resource test

Columbia drilling points to a larger resource envelope

Sentinel Metals Limited (ASX:SNM) has finished a 15-hole drilling campaign at its Columbia gold-silver project in Montana with two immediate tests ahead: whether the remaining assays support a larger November resource estimate, and how much of the newly identified mineralisation can sit inside an economic pit shell.

The strongest result remains the company’s first hole. Fire assays confirmed 46.8 metres at 5.33g/t gold from 88.2 metres in DDCO26-001, including 21.4 metres at 10.6g/t and 13.5 metres at 15.7g/t. On Sentinel’s standard compositing parameters, the interval becomes 38.9 metres at 6.28g/t, including 13.5 metres at 15.7g/t. The highest-grade subinterval, however, had average core recovery of only about 20%, a material qualification when assessing its representativeness.

The result sits alongside the stacked Columbia gold zones reported earlier in the campaign. DDCO26-003 returned a broader 48-metre composite at 1.13g/t, incorporating 6.1 metres at 3.50g/t and a 1.5-metre section at 12.1g/t. Northern holes also returned shallow mineralisation beyond the current resource pit shell, including 9.1 metres at 2.56g/t from 138.5 metres in DDCO26-010, with a 2-metre high-grade section at 9.44g/t.

November MRE will test tonnes, grades and pit limits

Sentinel says 11 of the 15 holes had been reported when the quarterly was finalised, leaving assays from DDCO26-012 to DDCO26-015 outstanding, along with additional fire assay and silver and multi-element results. The updated Columbia Mineral Resource Estimate is targeted for November 2026, subject to receiving and interpreting that remaining data.

Columbia’s existing JORC 2012 resource stands at 21.4 million tonnes at 1.3g/t gold for 920,000 ounces, constrained within a US$2,200/oz open-pit shell. The latest drilling also confirmed gold below the oxide zone and beyond the shell’s northern edge, but the resource remains entirely Inferred. The November update therefore matters not simply for a headline ounces figure, but for the extent to which drilling changes confidence, grade distribution and the shape of the potential open pit.

Big Springs adds a second Nevada development platform

The quarter also changed Sentinel’s scale. The company completed its acquisition of the Big Springs Gold Project in Nevada on 26 August, adding a 1.01 million-ounce JORC resource at 15.5 million tonnes grading 2.0g/t gold. Big Springs includes a permitted mine plan for open-pit and underground operations and has a production history of approximately 386,000 ounces from seven open pits between 1987 and 1993.

The acquisition, which followed the Big Springs acquisition funding, was funded through A$8.5 million in cash, 8,620,690 Sentinel shares valued at A$5 million at the placement price, and the potential for up to A$12.5 million in contingent consideration tied to specified milestones. Near-term work is focused on data review and planning, including the North Sammy target, where historical drilling included 18.3 metres at 33.4g/t gold from 129.5 metres. Sentinel says the system remains open at depth, but the company has not yet reported a new drilling campaign at Big Springs in this quarterly.

Royalty option offers flexibility but leaves a future decision

Sentinel has also secured an option to acquire Amazon Mining Company’s 1% production royalty over 13 patented Columbia claims hosting approximately 500,000 ounces of the current resource. The fixed price is 500 ounces of gold, with annual option payments of five ounces credited against that amount. If exercised, Sentinel says the resource-weighted effective royalty would fall from about 3.8% to 3.2%.

The option has not been exercised, and Sentinel can terminate it without penalty. The company expects the decision to be considered around a future Final Investment Decision, leaving the November resource update, permitting and development studies to inform whether the future royalty reduction justifies the eventual balloon payment.

Cash position leaves limited room for a higher-spending phase

Sentinel ended September with A$6.08 million in cash after A$10.78 million of investing cash outflows during the quarter, including A$2.17 million on exploration and evaluation. The quarter’s A$15 million equity raising, less A$971,000 in transaction costs, provided the principal financing inflow.

On the Appendix 5B calculation, the company has about two quarters of funding based on relevant outgoings of A$3.03 million for the quarter. Sentinel says it does not expect that cash-outflow rate to continue because the Columbia phase-one drilling program has concluded. That provides some relief, but the next phase will still need to balance Columbia’s pending resource work, Big Springs planning and any follow-up drilling against a cash balance that is not large by the standards of a two-project US gold strategy.