Iltani Resources Preps Isabel Drill Program as Historical Core Shows 654 g/t Indium
Key Takeaways
- Iltani received assay results from Union Jack RC drilling confirming sulphide mineralisation across all three holes, including 4m @ 5.5 g/t Ag and 2.3 g/t In from 166m in UJRC0002 and 14m @ 2.5 g/t Ag and 0.8 g/t In from 5m in UJRC0003.
- Physical review of historical Isabel diamond core at the Geological Survey of Queensland confirmed massive sulphide mineralisation with headline intercepts including 8.38m @ 250 g/t Ag, 660 g/t In, 0.7% Sn, 1.0% Cu, 1.6% Pb and 9.5% Zn from 37.49m in DMI-10.
- Diamond drilling at Isabel and Isabel Extended is expected to commence within one week of the 25 September 2026 announcement, with 10 holes planned for approximately 1,800m total across three 50m-spaced traverses.
- The Orient Silver-Indium Project — the regional processing hub anchor — has reached hole ORR243 of a planned 110-hole program, with completion expected within two weeks and the next drilling phase already being planned.
- The Orient JORC Mineral Resource stands at 62.5 Mt @ 81.5 g/t Ag Eq., comprising 38.8 Mt Indicated and 23.7 Mt Inferred, providing the economic backbone for the multi-target satellite strategy.
Iltani advances on multiple fronts at Herberton as Isabel drilling prepares to launch
Iltani Resources (ASX: ILT) has received assay results from its Union Jack and Boonmoo drilling programs, physically confirmed exceptional high-grade polymetallic mineralisation in historical Isabel diamond core, and announced that diamond drilling at Isabel and Isabel Extended is expected to commence within a week of this 25 September 2026 update. The three-pronged update reflects a systematic regional exploration campaign designed to identify satellite deposits within trucking distance of a potential Orient Silver-Indium processing plant.
The strategy is straightforward: define high-grade base metal-silver-indium resources at multiple nearby targets that could be treated through a future Orient plant, adding material value to the broader Herberton Project.
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Union Jack drilling validates the Boonmoo Sag Caldera system
Three RC holes (UJRC0001 to UJRC0003, 666m total) were completed to test VTEM geophysical targets and historical workings at Union Jack. Sulphide mineralisation was intersected in all three holes — notable because the area had no surface expression of mineralisation at depth and these represent the first drill holes in the central Boonmoo Sag Caldera since the 1980s.
Earlier geophysical work had already flagged the prospectivity of the Boonmoo Sag Caldera, with sulphide mineralisation across Union Jack confirmed over a 1,230-metre corridor prior to this latest round of RC drilling.
Two material intersections were returned:
- UJRC0002: 4m @ 5.5 g/t Ag, 2.3 g/t In, 0.30% Cu, 5.75% S from 166m
- UJRC0003: 14m @ 2.5 g/t Ag, 0.8 g/t In, 0.16% Pb, 0.17% Zn, 2.7% S from 5m
These results confirm the presence of a sulphide-rich system within the caldera complex. They do not represent economic grades at this stage, and further delineation work is required. Holes UJRC002 and UJRC003 have been lined with PVC pipe in preparation for a planned downhole electromagnetic (DHEM) survey. DHEM provides finer spatial resolution than airborne EM, allowing the team to better define the geometry and extent of the mineralisation at depth before planning the next phase of drilling.
Managing Director Donald Garner
“We now know the Union Jack system hosts sulphide-rich mineralisation – we just have to work our way through the system to find the economic grades.”
What is polymetallic massive sulphide mineralisation?
Massive sulphide mineralisation refers to dense concentrations of sulphide minerals (such as galena, sphalerite, and chalcopyrite) formed in rock. When a deposit carries multiple metals simultaneously (silver, zinc, lead, copper, tin, and indium in Iltani’s case), it is described as polymetallic — and that multi-metal profile is what makes these systems attractive exploration targets, since revenue potential spans several commodities.
Indium is particularly significant. It is classified as a critical mineral and is essential in touchscreens (as indium tin oxide) and, increasingly, in AI data centres where indium phosphide (InP) is used to manufacture laser chips that power high-speed optical transceivers. Iltani’s strategy of testing satellite targets within trucking distance of a potential Orient processing plant is logical: multiple deposits feeding one plant can materially improve overall project economics compared to a single-source operation.
Isabel historical core confirms exceptional grades — drilling imminent
Iltani physically reviewed historical diamond core from the Isabel deposit held at the Geological Survey of Queensland’s Exploration Data Centre in Zillmere, QLD. The review confirmed the visible, massive sulphide nature of the mineralisation (hosted in quartzites) and validated the exceptional grade profile recorded in historical assay data.
The headline intercepts from drill hole DMI-06, taken directly from Table 3 of the announcement, are:
- DMI-06: 4.27m @ 168 g/t Ag, 654 g/t In, 0.5% Sn, 1.1% Cu, 1.6% Pb & 30.7% Zn from 67.36m
- DMI-06: 5.18m @ 100 g/t Ag, 363 g/t In, 0.4% Sn, 0.8% Cu, 0.4% Pb & 20.4% Zn from 74.52m
Supporting evidence of grade consistency comes from DMI-10, which returned 8.38m @ 250 g/t Ag, 660 g/t In, 0.7% Sn, 1.0% Cu, 1.6% Pb & 9.5% Zn from 37.49m.
| Hole ID | Intersection | Key Grades | Depth (from) |
|---|---|---|---|
| DMI-06 | 4.27m | 168 g/t Ag, 654 g/t In, 0.5% Sn, 1.1% Cu, 1.6% Pb, 30.7% Zn | 67.36m |
| DMI-06 | 5.18m | 100 g/t Ag, 363 g/t In, 0.4% Sn, 0.8% Cu, 0.4% Pb, 20.4% Zn | 74.52m |
| DMI-10 | 8.38m | 250 g/t Ag, 660 g/t In, 0.7% Sn, 1.0% Cu, 1.6% Pb, 9.5% Zn | 37.49m |
All intersections are downhole widths only. Historical drilling cannot be used for JORC-compliant Mineral Resource estimation due to missing data such as accurate collar locations, downhole deviation surveys, and analytical certificates.
What’s next — Isabel and Isabel Extended drilling program
Iltani has outlined the following planned program, with Isabel diamond drilling expected to commence within one week of this announcement:
- Isabel: 10 diamond drill holes planned for approximately 1,800m total, drilled on three 50m-spaced traverses targeting mineralisation defined by historical intercepts.
- Historical drilling tested to 90m depth; Iltani will drill to 150m, with initial holes extended eastward to determine whether a second parallel lode exists approximately 50m east of the main lode.
- Isabel Extended: 1 diamond drill hole planned to approximately 200m depth, oriented west at -80° from the MIED 1 drill pad, targeting intersected mineralisation approximately 30m west. A DHEM survey will follow to define mineralisation geometry for subsequent drilling.
- Anniversary/St Patrick: Geochemical sampling and mapping planned to assess mineral species present, economic potential, and drill-readiness.
- Orient: Hole ORR243 underway (the 103rd of the planned 110-hole program); the current program is expected to be completed within 2 weeks, with the next phase of Orient drilling being planned.
Managing Director Donald Garner
“Based on the excellent results to date, we are planning the next phase of Orient drilling. More drilling delivering more tonnes, more grade and more metal as we grow the Orient Mineral Resource.”
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The bigger picture — Orient as the processing hub anchor
The Orient Silver-Indium Project underpins the regional exploration strategy. Drilling completed by Iltani since June 2023 has defined a JORC Mineral Resource of 62.5 Mt @ 81.5 g/t Ag Eq. (23 g/t Ag, 12 g/t In, 0.6% Pb & 0.7% Zn), comprising 38.8 Mt Indicated and 23.7 Mt Inferred (at a 30 g/t Ag Eq. cut-off grade), as detailed in Table 6 of the announcement.
The regional satellite targets at Isabel, Isabel Extended, and Union Jack are designed to be additive to this base. Should those deposits prove economic, the intent is that they could be processed through a future Orient plant, potentially improving overall project economics by spreading fixed infrastructure costs across a larger combined resource base.
For investors wanting to track the drill-hole-by-drill-hole progression of the Orient program as it approaches completion, our detailed coverage of recent Orient assay results walks through the highest-grade intercepts from the current campaign alongside their implications for the next resource update.
Ready to Explore Iltani’s High-Grade Silver-Indium Discovery at Herberton?
With exceptional historical grades confirmed at Isabel — including intercepts of up to 250 g/t Ag and 660 g/t In — and diamond drilling set to commence imminently, the Herberton Project’s multi-target strategy is rapidly taking shape. The broader regional vision, anchored by the 62.5 Mt Orient Silver-Indium Mineral Resource, positions Iltani as a compelling polymetallic exploration story at a critical juncture.
To track the Isabel drilling program as it unfolds and analyse what it could mean for the project’s overall resource potential, explore Iltani Resources’ full project profile on Discovery Alert for the latest updates and investment insights.