Dart Mining Sends Drills Below 160m for First Time at Victoria’s Top Tin Mine
Key Takeaways
- Dart Mining's 1,500m diamond program at Walwa starts the week of 12 October 2026, testing a tin system that has never been drilled below 160m.
- Walwa has the highest recorded primary tin production in Victoria, with about 97,000 t of ore treated in the late 1960s, yet historic holes averaged only about 50m deep.
- The targets include deeper aplite-pegmatite dykes, up to four seismic-interpreted dykes, and a conceptual greisen target 400m to 600m below surface.
- A June 2026 rock chip returned 3.96% Sn, and historic hole UP0016 hit 9m at 0.38% SnO₂ from 89m.
- The 1982 and 1983 historical estimates are pre-JORC and not treated as current resources, so assays from the nine permitted drill pads are the real catalyst.
Maiden drilling at Walwa Tin Project to test tin system below 160m
A 1,500m diamond drilling program at the Walwa Tin Project (EL007426, Northeast Victoria) is scheduled to commence in the week of 12 October 2026, according to an ASX release dated 7 October 2026 from Dart Mining NL (ASX:DTM). The system has never been drilled below 160m.
The program moves Dart Mining’s priority project from data review and sampling into the drill phase. It will test two never-drilled targets beneath the historic Walwa (Mt Alwa) tin mine for continuity of mineralisation at depth.
The company says Walwa has the highest recorded primary tin production in Victoria, with approximately 97,000 t of ore treated from the open pit in the late 1960s. It is described as the first diamond drilling at Walwa in decades.
James Chirnside, Chairman
“The start of drilling at Walwa is a milestone for Dart Mining…”
For investors, a first deep test of an established tin system is a clear catalyst. Assay results are expected to follow once received and compiled, and that is where the news flow will come from.
What the drill program targets
The program is aimed at three styles of target:
- Tin-mineralised aplite-pegmatite dykes at depth, below historically mined and drilled dykes
- Up to four additional dykes interpreted from a seismic survey
- A conceptual greisen target at the top of the interpreted causative intrusion, estimated to lie 400m to 600m below surface
Keep the distinction clear. The greisen target is conceptual, and the seismic dykes are interpretations, not confirmed mineralisation. Drilling is how those ideas get tested.
Drill pads and program design
Nine drill pads have been surveyed by DGPS and permitted along the existing access track network around the historic workings. The tracks were inspected in June 2026 and are in good condition for drill rigs and support equipment.
Each pad was positioned to allow multiple holes if required, which gives the company flexibility to expand the program.
The first holes target the pit area, where the dyke system is best known. They are designed to intersect the known dykes, test for repeating dykes at depth and continue towards the top of the interpreted intrusion. The sequence and depth of later holes will be guided by the geology seen in the first holes.
All core will be logged, photographed and sampled. Samples will be assayed for tin, tantalum, niobium and a multi-element suite, with results reported to the market when received and compiled.
When big ASX news breaks, our subscribers know first
Why Walwa matters: a historic tin field never tested at depth
Tin was first mined at Walwa in 1882, with intermittent mining continuing until the late 1960s. Ore came from shallow dipping, tin-bearing aplite-pegmatite dykes up to 8m thick, which carry coarse cassiterite (the primary ore mineral of tin) along their margins.
Yet the system was never fully tested. Dart Mining has compiled and verified 150 historic drill holes totalling 7,672m, mostly shallow percussion holes drilled in the 1970s and 1980s. The deepest reached 160m, against an average depth of about 50m.
The table below shows selected reported intercepts from that historic drilling, plus the June 2026 rock chip. These are previously reported results, not new data.
| Hole or sample | Result | From depth | Source type |
|---|---|---|---|
| UP0016 | 9m @ 0.38% SnO₂ | 89m | Historic drilling |
| DDH2 | 6.1m @ 0.58% SnO₂ | 35.1m | Historic drilling |
| WRC0013 | 18m @ 0.18% SnO₂ | 42m | Historic drilling |
| WWP002 | 3.96% Sn, 165 ppm Ta, 197 ppm Nb | Surface | Rock chip (June 2026) |
The WWP002 sample came from in-situ pegmatite on the south-west wall of the pit. Other samples in the batch graded 0.40% to 1.09% Sn, and earlier rock chips returned up to 2.91% Sn at Mt Alwa South and up to 670 ppm Ta at Snake Gully.
Alderan Resources concluded in 2014 that historic drilling may have penetrated only the top margins of a larger mineralised body, with grades increasing at depth. That is Alderan’s view, and it is what the new program sets out to test.
Historical estimates
Union Corporation reported two historical pre-JORC estimates at Walwa: 8.64 Mt at 0.163% Sn and 50 ppm Ta₂O₅ (March 1982) and 993,000 t at 0.38% Sn and 55 ppm Ta₂O₅ (September 1983).
Cautionary statement
These are historical estimates. They were not prepared under the JORC Code 2012 and the Company is not treating them as current Mineral Resources. Refer to the 25 August 2026 announcement for the information required under ASX Listing Rule 5.12.
How can buried granite and greisen host tin?
Greisen is a rock formed when granite is altered by hot, mineral-rich fluids. In similar tin systems around the world, tin-rich fluids collect at the roof of the granite and alter it to greisen, which can host large, high-grade deposits such as those of the Altenberg district in Germany.
The sequence works in three steps:
- A tin-bearing granite sits at depth.
- Tin-rich fluids collect at the roof of that granite.
- The fluids alter the granite to greisen, which can host large, high-grade deposits.
Dart Mining’s interpretation is that earlier explorers recorded unidirectional solidification textures in the dykes, along with outward zoning of tantalum and niobium away from the pit. The company reads these features as evidence of a buried granite cupola beneath the pit. The dykes are described as a highly fractionated offshoot of the Silurian Koetong Granite, part of the Wagga Tin Belt.
This is a hypothesis, not a result. If drilling supports it, depth could change the scale of the Walwa story, and if it does not, investors will know that too.
The next major ASX story will hit our subscribers first
Next steps and portfolio upside
The announcement sets out the following next steps:
- Commence diamond drilling at Walwa in the week of 12 October 2026.
- Provide regular updates as drilling progresses, including geological observations from the core.
- Report assay results when they are received and compiled.
- Carry out systematic rock chip and channel sampling of the tantalum-enriched albitite dykes at Snake Gully for total Sn, Ta and Nb.
- Conduct field inspection and rock chip sampling of the McHargs tungsten and Hall’s gold prospects to confirm the historical results and plan future drilling activity.
Dart Mining also notes additional tungsten potential at the McHargs and Koetong prospects, where it is advancing targeting work and planning for maiden drilling. Historic non-JORC Resource declarations at McHargs Tungsten are covered in its 11 August 2026 release and should be read with the same cautionary framing as the Walwa estimates.
Beyond Walwa, which is 100% owned, the portfolio includes the Triumph Gold Project in central Queensland. Triumph hosts an Inferred JORC 2012 Mineral Resource of 150koz at 2.1 g/t Au, giving the company a gold asset alongside its tin exploration.
Get Tin and Mining News Before the Market Moves
Get FREE breaking ASX mining news delivered to your inbox within minutes of release, complete with in-depth analysis. Join 30,000+ investors already receiving real-time alerts. Click the “Free Alerts” button at Big News Blast to stay ahead when the next market-moving announcement lands.