Dart Mining Identifies High-Grade Tin Signal at Walwa Ahead of Drilling
Dart Mining has confirmed high-grade tin in four selective rock-chip samples from its Walwa project in Northeast Victoria, including 3.96% tin with elevated tantalum and niobium. The results strengthen the case for maiden diamond drilling planned for October, but do not establish representative grades or a mineral resource.
- 3.96% tin from an in-situ cassiterite-bearing pegmatite sample
- Four samples returned between 0.40% and 3.96% tin
- Elevated tantalum, niobium, lithium, rubidium and caesium support a fractionated pegmatite interpretation
- Maiden diamond drilling planned across nine sites from October 2026
- Selective grab samples cannot establish average grades or mineralisation continuity
3.96% Tin Sample Sets Walwa Benchmark
A rock sample from the wall of Dart Mining NL’s (ASX:DTM) historic Walwa open pit returned 3.96% tin, giving the company its strongest modern assay yet from the Northeast Victorian tin field. The in-situ grab sample, WWP002, also contained 165 parts per million tantalum and 197 ppm niobium, with coarse black cassiterite visible in the pegmatite.
Three other samples collected in June returned between 0.40% and 1.09% tin. A greisenous pegmatite boulder from the pit floor graded 1.09%, float north of the pit returned 0.61%, and an outcrop sample from the Mt Alwa South prospect, about 700 metres south, graded 0.40%.
Assays Point to Fractionated Tin-Tantalum System
All four samples were enriched in lithium, rubidium and caesium, elements Dart says are consistent with a highly fractionated rare-metal pegmatite system. Rubidium reached 2,611 ppm and caesium 156 ppm in the northern float sample, while tantalum and niobium generally increased with tin grade. Tungsten was low at no more than 9 ppm, supporting the company’s interpretation that Walwa is primarily a tin-tantalum system rather than a tin-tungsten deposit.
The results also fit a pattern in the historical record: tin grades are strongest around the Walwa pit, while tantalum and niobium appear more prominent farther out at Mt Alwa South, Redbank Creek and Snake Gully. Dart interprets that zoning, together with the geometry of the shallow-dipping dykes, as evidence of a buried granite source beneath the historic workings.
Selective Samples Leave Scale Unresolved
The headline grade comes with an important qualification. These were selective grab samples taken from visibly mineralised rock, including float and boulder material, and Dart states they are not representative of average dyke grades. The sampling confirms the presence of cassiterite and high-grade pockets, but says little by itself about width, continuity, recoverability or the size of any economic system.
Historical results provide useful support but carry their own limitations. Previous programs recorded up to 2.91% tin at Mt Alwa South and 0.44% tin with up to 670 ppm tantalum at Snake Gully, while a 2008 program reported an average of 0.23% tin across 80 samples from the Walwa pit area. Those historical results have not been independently verified by Dart through resampling or reassaying, and they are not mineral resources under the JORC Code 2012.
Diamond Drilling Scheduled for October
Dart plans to begin its maiden diamond drilling program in October, with preparations advanced across nine proposed sites. The program is designed to test repeated tin-bearing dykes at depth and a possible deeper greisen zone near the top of the interpreted causative intrusion. Access agreements and work plan approvals are still being progressed.
The drilling will be the more consequential test of the Walwa thesis. Until core provides measurable widths and repeatable grades, the 3.96% assay is best viewed as a compelling geological signal rather than evidence of a mineable deposit. Dart also intends to carry out systematic sampling at Snake Gully and Redbank Creek, alongside inspections of the McHargs tungsten and Hall’s gold prospects.
Bottom Line?
October’s drilling should determine whether Walwa’s high-grade surface samples extend into a coherent underground system or remain isolated pockets in a historic mining field.
Questions in the middle?
- Will diamond drilling confirm continuous tin-bearing widths beneath the Walwa pit?
- How will tin, tantalum and niobium grades vary between the central pit and outer prospects?
- Can Dart secure the required access and work approvals in time for the October program?
