Great Boulder Resources Expands Mulga Bill East Gold Mineralisation by 400m at Side Well Project

Extensional Drilling Confirms Grade Continuity Over Expanded Mulga Bill East Zone

Great Boulder’s recent drilling at Side Well has delivered multiple high-grade gold intersections, confirming consistent mineralisation across an expanded Mulga Bill East footprint. The extensional drilling targeted areas beyond the current resource boundary, focusing north and east of the existing 782,000 ounce Mulga Bill–Eaglehawk resource. Results confirm gold mineralisation over a significantly longer strike length than previously modelled, demonstrating grade continuity across several drill holes.

Notable results include 18 metres at 7.36 grams per tonne gold from 120 metres depth in hole 26MBRC039, approximately 140 metres north of the current resource boundary. Other significant intersections include 6 metres at 14.8 grams per tonne gold from 265 metres depth in hole 26MBRC034 and 2 metres at 13.3 grams per tonne gold from 102 metres depth in hole 26MBRC033. Additional results comprise 4 metres at 5.79 grams per tonne gold, 4 metres at 4.47 grams per tonne gold, 2 metres at 8.80 grams per tonne gold, and 8 metres at 2.08 grams per tonne gold from various depths and holes within the extended zone.

Eaglehawk Deposit Remains Open with Significant High-Grade Intercepts at Resource Margins

Drilling at Eaglehawk within the Side Well Project has focused on defining the mineral resource envelope’s margins. Results indicate mineralisation extends beyond previously modelled lodes and remains open outside current resource boundaries. The Eaglehawk program has returned several high-grade intersections, supporting further resource expansion potential.

Highlighted results include 7 metres at 14.5 grams per tonne gold from 56 metres depth in hole 26EHRC032, and an exceptional narrow intercept of 0.64 metres at 82.8 grams per tonne gold from 265.36 metres depth in hole 26EHRCD001. Additional intersections include 4 metres at 9.12 grams per tonne gold from 80 metres in hole 26EHRC027, 8 metres at 4.30 grams per tonne gold from 84 metres in hole 26EHRC026, and 4.05 metres at 8.08 grams per tonne gold from 110.15 metres depth in diamond hole 26EHDD002. The combined Mulga Bill–Eaglehawk deposit now extends over 2.5 kilometres strike length, with recent drilling confirming mineralisation bridging the gap between the two lode systems.

Ironbark Metallurgical Drilling Yields High-Grade Gold for Processing Studies

Great Boulder completed diamond drilling at the Ironbark deposit, a third significant mineralisation zone within the Side Well Project. This drilling aimed to obtain core samples for geotechnical and metallurgical testing, concluding a broader campaign started in late 2025. Ironbark contributes to Side Well’s mineral inventory and represents a potential future mining target.

Diamond hole 26IBDD001 intersected 5.89 metres at 18.1 grams per tonne gold from 106.5 metres depth. This high-grade intersection aligns with previous reverse circulation results defining mineralisation at Ironbark’s northern end. The metallurgical core will support process design and mineral processing studies as Side Well advances toward potential development.

Peak Hill Project Commences Active Drilling Phase Post Acquisition

Great Boulder has deployed two reverse circulation rigs at its recently acquired Peak Hill Gold Project, initiating active exploration and resource definition. The company plans 40,000 metres of drilling this half-year, with one rig at the Jubilee–Golden Treasure area and another at Durack. Peak Hill represents a second major gold project alongside Side Well.

Peak Hill hosts a 481,000 ounce gold resource, including 376,000 ounces indicated and 105,000 ounces inferred, based on 7.547 million tonnes at 1.5 grams per tonne gold (indicated) and 1.838 million tonnes at 1.8 grams per tonne gold (inferred). The drilling campaign aims to expand resources and identify extensions. First assay results are expected in late August 2026, offering early insights into mineralisation quality and distribution.

Side Well Project Advances Systematic Exploration Across Multiple Mineralisation Systems

The Side Well Gold Project near Meekatharra encompasses multiple mineralisation systems: Mulga Bill, Eaglehawk, and Ironbark, forming a complex gold system with multiple resource-hosting structures. The current resource totals 1.021 million ounces, comprising 626,000 ounces indicated and 395,000 ounces inferred across 16.042 million tonnes at an average grade of 2.0 grams per tonne gold. The diverse mineralisation offers multiple development and expansion opportunities.

Great Boulder operates a diamond rig at Golden Bracelet within Side Well, alongside an air core rig testing regional targets in the Eastern corridor. This combined approach targets definition drilling near known mineralisation and regional exploration to discover new gold systems. Ongoing drilling at Side Well and aggressive exploration at Peak Hill position the company to provide a steady flow of assay results and updates throughout the period.

Geological Framework Supports High-Grade Vein-Hosted Gold Mineralisation Model

Mineralisation at Side Well occurs within a well-defined geological framework dominated by west-dipping quartz veins and subvertical sulphide-rich lodes, the primary gold hosts. The Mulga Bill East zone, extended by over 400 metres, features these vein and lode styles that have historically yielded the highest grades. Drilling has refined the understanding of these structures’ 3D geometry, enabling targeted exploration of extensions and continuity.

Multiple intersections exceeding 10 grams per tonne gold highlight the mineralisation quality. Geological mapping using recent assay data confirms mineralisation extends significantly beyond current resource boundaries. Discovery of mineralisation in previously untested areas, such as the gap between Eaglehawk and Mulga Bill, indicates potential for ongoing resource growth through systematic exploration.

Resource Expansion Potential Evident from Extensional Drilling Beyond Current Limits

Great Boulder’s drilling strategy explicitly targets areas outside the current 1.02 million ounce resource boundary to define extensions for future resource updates. The 400-metre Mulga Bill East extension and mineralisation bridging Eaglehawk and Mulga Bill significantly expand Side Well’s mineralised footprint. These expansions lay groundwork for potential resource upgrades pending further drilling and JORC-compliant estimation.

Continued identification of high-grade gold outside current resource envelopes suggests additional gold inventory may be incorporated into future resource statements. Investors tracking Great Boulder’s progress should anticipate updates reflecting the latest drilling impact. The consistent discovery of extensions underscores Side Well’s strong exploration upside beyond the existing 1.02 million ounce resource.

Ongoing Exploration and Anticipated Timing for Assay Results

Great Boulder continues drilling at both Side Well and Peak Hill with multiple rigs active. At Side Well, a diamond rig operates at Golden Bracelet while an air core rig explores regional targets in the Eastern corridor, balancing definition and regional drilling. At Peak Hill, 40,000 metres of drilling is planned this half-year, with one RC rig at Jubilee–Golden Treasure and another at Durack.

Managing Director Andrew Paterson stated the company expects first assay results from Peak Hill in late August 2026, providing early insights into the new drilling campaign. The steady release of assay data from Side Well combined with imminent Peak Hill results will sustain investor engagement and market visibility. This dual approach of extensional drilling at mature deposits and regional exploration at new assets supports diversified growth across Great Boulder’s portfolio.