Astral Resources Hits High-Grade Gold Below Mandilla Resource Shell Pointing to MRE Growth
Key Takeaways
- Two new diamond drill holes at the Theia Deposit have returned significant gold intercepts both within and below the April 2026 MRE pit shell, with below-shell results averaging higher grades than material inside the shell.
- AMRCD375 returned 85.6 gram x metres at 1.67g/t Au below the resource boundary, while AMRCD424 added 107.7 gram x metres at 1.20g/t Au below the shell — both material in volume and grade.
- The Theia Deeps program has now completed 15 of 21 holes across 11,000m, with the mineralised system remaining open at depth across a strike length exceeding 1.6km.
- An MRE update incorporating both the Theia Deeps diamond drilling and the ongoing RC in-fill program (336 of 431 holes complete) is expected in the March Quarter 2027.
- The Mandilla PFS, based on a 2.75Mtpa processing facility producing 95koz per year, delivered an NPV8 of $1.4 billion at A$4,250/oz gold — rising to $2.9 billion at A$6,250/oz.
Theia Deeps results reveal high-grade gold well below the current resource shell
Astral Resources (ASX: AAR) has reported assay results from two further diamond drill holes at the Theia Deposit, part of the 100%-owned Mandilla Gold Project located 70km south of Kalgoorlie in Western Australia. The results from holes AMRCD375 and AMRCD424 confirm significant gold mineralisation both within and below the April 2026 Mineral Resource Estimate (MRE) pit shell, reinforcing the depth growth potential of the cornerstone 1.4Moz Theia Deposit.
These two holes form part of the expanded 21-hole, 11,000m Theia Deeps diamond drill (DD) program, with 15 of 21 holes now complete. The Theia Deposit sits within the broader 1.74Moz Mandilla Gold Project MRE (April 2026), making it the project’s anchor asset. The fact that mineralisation has been confirmed below the existing MRE pit shell is the key result here: it points directly to resource growth potential ahead of a planned MRE update.
Headline intercepts from AMRCD375:
- 22m at 2.73g/t Au from 361m, including 0.3m at 133g/t Au from 382.65m
- 5m at 9.92g/t Au from 120m, including 1m at 45.2g/t Au from 121m
- 49m at 0.90g/t Au from 284m, including 0.3m at 20.9g/t Au from 294.79m
Headline intercepts from AMRCD424:
- 49m at 1.23g/t Au from 252m, including 1.1m at 10.3g/t Au from 257m and 0.3m at 14.7g/t Au from 262m
- 2m at 12.8g/t Au from 390m, including 0.3m at 83.5g/t Au from 390.44m
- 5m at 4.14g/t Au from 380m, including 1m at 19.1g/t Au from 382m
- 21m at 0.76g/t Au from 575m
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What the results mean — mineralisation is growing at depth
Inside vs. below the resource shell — a key distinction
Not all intercepts carry the same strategic weight. The announcement distinguishes between results within the April 2026 MRE pit shell and those returned below it, and investors should understand why that distinction matters.
For AMRCD375, cumulative gram x metre within the MRE shell totalled 162.9 at an average grade of 1.21g/t Au. Below the shell, the hole returned a cumulative 85.6 gram x metres at an average of 1.67g/t Au, a higher average grade than the material inside the shell.
AMRCD424 followed a similar pattern. Within the MRE shell, the hole returned a cumulative 119.4 gram x metres at an average of 1.0g/t Au. Below the shell, the hole added 107.7 gram x metres at an average of 1.20g/t Au. Notably, AMRCD424 encountered a zone of reduced dilation from 100m down-hole, which restricted quartz vein propagation. Veining frequency subsequently increased from 250m down-hole, producing the significant intercepts deeper in the hole. This behaviour shows the mineral system re-opens at depth rather than closing off.
Both holes confirm that mineralisation below the existing resource boundary is not a minor tail — it is material in both volume and grade.
MD quote
Marc Ducler, Managing Director, Astral Resources
“The highly successful Theia Deeps drill program is continuing to confirm wide high-grade zones of gold mineralisation within the existing Mineral Resource shell, while also demonstrating significant growth potential at depth. The latest assay results from drill holes AMRCD375 and AMRCD424 confirmed broad zones of gold mineralisation both within the current MRE – such as 49m at 1.23g/t Au and 49m at 0.90g/t Au – and beneath the base of the current April 2026 Mineral Resource shell – such as 22m at 2.73g/t Au, 5m at 4.14g/t Au and 2m at 12.8g/t Au. Theia Deeps diamond drilling program and Theia RC in-fill program remain in progress. Assay results from both programs will support an update to the Mandilla MRE, likely to be scheduled in the March Quarter 2027.”
Understanding diamond drilling and what depth extensions mean for a gold resource
A Mineral Resource Estimate (MRE) is a formal, JORC-compliant calculation of the amount of gold sitting in the ground at a project, categorised by confidence level as Measured, Indicated, or Inferred. It is not a static number. As new drilling results come in, the estimate is updated to reflect what the ground is actually showing.
The MRE pit shell refers to the boundary used when calculating the current resource. Intercepts within that shell contribute to resource conversion — confirming or upgrading what is already counted. Intercepts below the shell are additive: they sit outside the current resource inventory and represent potential growth when the next MRE update is prepared.
Gram x metre is a straightforward measure. It is simply the length of a drill intercept multiplied by its grade. A result of 162.9 gram x metres tells you there is significantly more contained gold in that intersection than a narrower or lower-grade zone would carry. Higher gram x metre numbers mean more gold per unit of rock.
A deposit that remains open at depth — where drilling keeps finding gold below the lowest point of the current resource — is a deposit that may be larger than currently defined. The Theia Deeps program is specifically designed to test how far that system extends. The practical outcome is an MRE update expected in the March Quarter 2027, which will incorporate both the Theia Deeps DD results and the results from the ongoing Theia RC in-fill program.
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The bigger picture — Mandilla’s resource base and the path to MRE growth
Group resource and reserve snapshot
The Theia results build on an already substantial resource base across Astral’s three gold projects. The group’s consolidated JORC 2012 Mineral Resource Estimate, as reported in the announcement, is summarised below.
| Project | Total Tonnes (Mt) | Grade (g/t Au) | Total Ounces (oz Au) | Category |
|---|---|---|---|---|
| Mandilla | 53.5 | 1.0 | 1,736,000 | Measured + Indicated + Inferred |
| Feysville | 5.0 | 1.2 | 196,000 | Indicated + Inferred |
| Spargoville | 3.0 | 1.4 | 139,000 | Indicated + Inferred |
| Group Total | 61.6 | 1.0 | 2,072,000 | All Categories |
The group’s consolidated Ore Reserve stands at 1,082,000oz, comprising 1,000,000oz at Mandilla and 88,000oz at Feysville, both classified as Probable.
What’s driving the drill program expansion
The Theia Deeps program has been expanded on multiple occasions since its original scope, reflecting the ongoing success of each drill campaign. It now encompasses 21 holes for 11,000m. The Theia mineralised footprint extends over a strike length of more than 1.6km, and the Deeps program is now focused on testing both the width and strike of the deeper mineralisation discovered to date.
Context from the Mandilla Preliminary Feasibility Study (PFS), announced in June 2025, underscores what is at stake. The PFS was based on a standalone project comprising a 2.75Mtpa processing facility producing 95koz per year for the first 12 years. At a base case gold price of A$4,250/oz, the PFS demonstrated an NPV8 of $1.4 billion. At A$6,250/oz, the NPV8 increases to $2.9 billion.
Near-term milestones to watch:
- 15 of the 21 holes in the DD program have been completed
- RC in-fill program: 336 holes for 23,900m complete of the 431-hole (44,400m) program
- Heritage surveys for Kamperman (Feysville) and Spiders Deposits (Spargoville) completed; drill pad preparation being scheduled, with drilling planned to commence early in the December Quarter 2027
- MRE update: likely scheduled for the March Quarter 2027, incorporating both DD and RC in-fill results
Ready to Explore the Depth Growth Potential at Astral Resources’ Theia Deposit?
The Theia Deeps drill program is delivering high-grade gold intercepts both within and below the current resource shell, with results such as 22m at 2.73g/t Au pointing to a resource base that may be materially larger than currently defined. An MRE update is expected in the March Quarter 2027, incorporating results from the ongoing diamond and RC in-fill programs across the 1.74Moz Mandilla Gold Project.
To understand the full scale of the opportunity, including the project’s $1.4 billion NPV8 and the drilling milestones still to come, explore the Astral Resources (ASX: AAR) investor profile on Discovery Alert for the latest updates and project details.