ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 1 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU TRANSFORMATIONAL ACQUISITIONOF NEIGHBOURING PEAKHILL GOLD PROJECT HIGHLIGHTS ➢ Great Boulder has entered into a binding agreement to acquire 100% of Westgold’s interest1 in the Peak Hill Gold Project in Western Australia, proximal to Westgold’s three mills – Bluebird, Fortnum, and Tuckabianna, and only 100km from Great Boulder’s Side Well Gold Project ➢ Peak Hill is an historic high-grade production centre with past production in excess of 900,000oz, four historic open pit mines and seven granted mining leases ➢ Peak Hill hosts a JORC 2012 Mineral Resource Estimate of 9.4Mt @ 1.6g/t Au for 481,000oz (further information below) ➢ Great Boulder considers Peak Hill to be extremely prospective, with potential to significantly increase the known gold endowment as well as numerous near-mine and brownfields exploration opportunities ➢ Great Boulder and Westgold have entered into an Ore Purchase Agreement (OPA) to process ore at one or more of Westgold’s three mills in the region, focused on a capital light, near-term production model ➢ Great Boulder and Westgold have formed a Non-Binding Strategic Collaboration to evaluate options that could fast track Great Boulder’s 1Moz Side Well Gold Project, only 25km from Westgold’s neighbouring Bluebird Mill ➢ Great Boulder intends to complete a combined 60,000 metre, multi-rig drilling campaign at both projects over the next six months ➢ The Company aims to deliver an updated Mineral Resource Estimate at Peak Hill in 6 months ➢ Aim to have Peak Hill in‘’Mining-Ready’’status under the OPA within 12 months of completion2 ➢ GBR has already started preparing for pre-production activities with the employment of Chris Tuckwell as Chair, who was the MD of Australia's largest open pit mining contractor Details of the Transaction ➢ Great Boulder to acquire the Peak Hill Gold Project from Westgold for $25 million in cash, a 19.9% shareholding in Great Boulder and a 1% NSR royalty interest ➢ Concurrent with the Acquisition, Great Boulder is undertaking a Placement pursuant to which it is seeking firm commitments from institutional investors, including leading domestic and global institutions, to raise $40 million via a two-tranche placement at 8.5c per share. ➢ Following the completion of the Acquisition and Placement Great Boulder will be very well positioned, with a strong pro-forma net cash balance of $25m, to fund an aggressive drilling ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 2 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU campaign across the Peak Hill Gold Project and the Side Well Gold Project, and engineering studies and activities 1. 7 granted mining leases (four 100% owned, three 85% owned), 1 granted exploration license (85% owned) – see Acquisition Terms and Table 3 below. 2. Aspirational statements: The statements which appear in this presentation regarding the aspirations for the Company to achieve “mining-ready” status for the Peak Hill Gold Project are aspirational statements. These statements are not production targets nor mineral resource estimates. The statements are considered aspirational because the Company has not yet completed sufficient work to update mineral resource estimates or undertake economic studies. Great Boulder Resources Limited (“Great Boulder” or the “Company”) (ASX: GBR) is pleased to announce that it has agreed to acquire the Peak Hill Gold Project (“Project”)(“Acquisition”) from Aragon Resources Pty Ltd, a wholly owned subsidiary of Westgold Resources Limited (ASX:WGX)(“Westgold”). Consideration for the Acquisition will consist of a mixture of a deposit, cash consideration and consideration shares. 391.7 million fully paid ordinary shares (‘’Consideration Shares’’) in Great Boulder will be issued to Westgold such that Westgold will hold 19.9% of the shares on issue in Great Boulder post the Transaction completion and post Placement completion. The total cash consideration is $25 million (‘’Cash Consideration’’). Great Boulder has paid a $1 million deposit and the balance of the cash consideration of $24 million is payable on completion. An NSR royalty interest of 1% on the production of gold from the Project tenements will be granted to Westgold on Completion. In addition, Westgold will have the right to nominate a board representative to the Great Boulder Board. The shareholding interest, along with the Ore Purchase Agreement and the Strategic Collaboration provide for a long term mutually beneficial relationship that has the potential to deliver enhanced shareholder value for both Great Boulder and Westgold shareholders. Westgold’s decision to take a 19.9% shareholding in Great Boulder reflects confidence in both the potential of the Peak Hill Gold Project, Great Boulder’s Side Well Gold Project and in Great Boulder’s ability to progress the two neighbouring Projects. The Acquisition provides a material uplift in the Great Boulder gold resource inventory and provides a pathway to capital light gold production in the near term. The recent Board appointment of Chris Tuckwell, former Managing Director of leading mining contractor MACA Limited, complements the experienced Board and management team and places the Company in a strong position to progress the projects towards production. Great Boulder Managing Director, Andrew Paterson, said: “The acquisition of the Peak Hill Gold Project is hugely transformational for Great Boulder. Not only does it add a significant gold endowment to our existing Side Well Gold Project but with the ore purchase agreement and support of leading gold producer Westgold Resources it places us on a pathway to capital light production.’’ ‘’Following completion of the acquisition and completion of the Placement we will be well funded with $25 million cash at bank and the next 6-12 months will be milestone rich as we execute aggressive drilling campaigns (with up to 6 rigs planned – across Peak Hill and Side Well, for 60,000m of drilling) and progress pre-production activities. We aim to have an updated mineral resource estimate in respect of Peak Hill within 6 months and to advance down the pathway to capital light production, all the while potentially fast-tracking Side Well in Strategic Collaboration with Westgold towards capital light production.’’ Westgold Managing Director, Wayne Bramwell, said: ‘’Westgold has high regard for its Murchison goldfields neighbour, and their commitment to becoming a miner. ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 3 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU As such Great Boulder is a logical choice as a future production partner for the Peak Hill Gold Project. Westgold continues to support smaller companies in their journey to being producers across WA and looks forward to assisting Great Boulder with a capital light opportunity that leverages our extensive Murchison processing infrastructure. In addition to a definitive agreement on Peak Hill, we have signed a Strategic Collaboration agreement with Great Boulder to jointly evaluate opportunities that could assist in the development of the Side Well Gold Project.’’ Peak Hill Gold Project Overview The Peak Hill Gold Project is strategically located in the Northern Murchison Goldfields of Western Australia approximately 120km from Meekatharra and within trucking distance of multiple processing facilities, only 100km from Great Boulder’s Side Well Gold Project. Project tenure includes seven granted mining leases, one granted exploration licence and seven miscellaneous licences for infrastructure such as haul roads and an airstrip. Total area of mining tenure is 106km2 . Figure 1: Peak Hill is 100km from Side Well, 50km from the Fortnum mill and 120km from Bluebird ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 4 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU Much of the known gold mineralisation at Peak Hill is hosted within five main deposits: Five Ways, Durack, Enigma, Harmony and Jubilee. These host a JORC 2012 Mineral Resource Estimate of 9.4Mt at 1.6 g/t Au for 481,000oz1 of contained gold, as shown in Table 1 below. Additional disclosure pursuant to the reporting requirements for Mineral Resources and Exploration Results and Exploration Targets is detailed in Annexure A starting on page 21. TABLE 1: PEAK HILL RESOURCE ESTIMATES AS REPORTED Peak Hill Mineral Resources Deposit Classification Tonnes Grade Ounces Cut-off parameters Harmony Indicated 939,000 1.8 55,000 Reported at 0.8g/t Au above a pit shell Inferred 66,000 3.5 7,000 Subtotal 1,005,000 1.9 62,000 Enigma Indicated 444,000 1.8 26,000 Reported at 0.7g/t Au above a pit shell Inferred 260,000 1.8 15,000 Subtotal 704,000 1.8 41,000 Jubilee Indicated 99,000 1.9 6,000 Reported at 1.0g/t Au above a pit shell Inferred 371,000 2.4 29,000 Subtotal 470,000 2.3 35,000 Durack Indicated 2,309,000 1.2 89,000 Reported at 0.8g/t Au to 150m from surface Inferred 580,000 1.2 23,000 Subtotal 2,889,000 1.2 112,000 Fiveways Indicated 3,756,000 1.6 199,000 Reported at 0.8g/t Au above 435RL; 2g/t Au below 435RL Inferred 561,000 1.7 31,000 Subtotal 4,317,000 1.7 230,000 Total Indicated 7,547,000 1.5 376,000 Inferred 1,838,000 1.8 105,000 Subtotal 9,385,000 1.6 481,000 Please refer to the JORC Table 1 on page 42 below for details on the data and estimation techniques applicable to each resource estimate. There has been historical production of more than 900koz of gold across multiple mining areas, including historical underground mining until 1913 and modern open pit mining active between 1988 and 19972 . There has been no mining at Peak Hill since 1997. Given the current strong gold price environment a preliminary assessment by Great Boulder’s technical team supports the view that there is significant upside potential to extend these five estimates once sufficient work has been completed. The Company is planning an intensive drilling campaign designed to allow the estimation of an updated Mineral Resource Estimate within six months of completing the acquisition. 1 Refer to Table 1 and the JORC Table 1 (from page 42) 2 Westgold internal memo:“Peak Hill Gold Project History” ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 5 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU Figure 2: The Peak Hill Project includes seven granted Mining Leases and one Exploration Licence Of the 15 individual tenements (one granted Exploration Licence, seven granted Mining Leases and seven Miscellaneous Licences for infrastructure) Great Boulder will hold 100% interest in 11 of them and an 85% joint venture interests in 4 tenements. A summary of the tenements and joint venture interests is listed in Table 3. Five Ways Deposit The FiveWays deposit, located 130kmnorth of Meekatharra, is the largest deposit and historical mining centre of the Peak Hill Gold Project with previous production of 680koz from open pit and underground mining. ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 6 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU Mineralisation consists of quartz veins with strong biotite alteration, forming lodes sub-parallel to low-angle thrust surfaces on the west limb of an antiform with continuation of the thrust system at depth to the west. The last drilling at Five Ways was in October 2015 when 17 holes were drilled for a total of 1,169 metres. Gold mineralisation remains open down plunge and along strike, with only a small number of holes drilled along strike immediately north of the current pit. Figure 3: Plan view of the Five Ways area showing previous drilling coloured by maximum down-hole Au (g/t) Jubilee Deposit Jubilee deposit sits along strike from and approximately 2km north of Five Ways. Gold mineralisation is hosted within a complex quartz stockwork on the contact between Peak Hill hangingwall sequence and a dolerite dyke. Drilling defines shallow north-dipping lodes flattening away from the dolerite contact, which folds around the eastern and northern areas of Jubilee and then west towards the Slingshot prospect. There is little drilling along this prospective horizon between Five Ways and Jubilee. ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 7 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU Figure 4: Plan view of the Jubilee area showing a conceptual pit outline with previous drilling coloured by maximum down-hole Au (g/t) Harmony Deposit Harmony is located 9km west of Five Ways and less than 2km from the Fortnum access road. Gold mineralisation is hosted at the contact between the Narracoota Formation (mafic-ultramafic volcanic rocks) and the Ravelstone Formation. Mineralisation is thought to remain open along strike to the north, with approximately 100m between the last line of RC drilling within the pit and the next line of AC holes. This will be an early drill target for Great Boulder with potential for a northern cutback to the existing Harmony pit. ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 8 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU Figure 5: Plan view of Harmony pit & Enigma trend showing previous drilling coloured by maximum down-hole Au (g/t) Enigma Deposit The Enigma deposit is located 7km southwest of Five Ways and 3km southeast of Harmony, with no previous mining undertaken. Mineralisation at Enigma is interpreted to be deeper, quartz vein hosted, sulphide mineralisation striking towards 330º magnetic grid and dipping at 50-60º to the west. There is also some shallow oxide mineralisation. Enigma lies on the hinge of an anticline striking towards 310º. The mineralised trend extends for 5km, with the highest concentration of gold mineralisation in Enigma and Enigma North adjacent to Harmony. The last reported drilling was 4 RC holes drilled in 2010 for 509m. Durack Deposit The Durack and neighbouring Windsor deposits sit 13km south of Five Ways and have not been previously mined. Gold mineralisation is associated with steeply dipping quartz veins on margins of pyrite alteration with stratigraphic control (volcanic and sedimentary interbedding rocks) and steep dips to the northeast. Despite the estimation of a historical resource for Durack and Windsor in 2011 the area remains relatively under- explored, and there is an excellent likelihood that additional drilling will identify extensions to the deposits along strike and down dip. With gold intersected in previous drilling along the same trend 1.7km northwest at Murphy Creek and anomalous gold assays in surrounding historic RAB drilling the Company considers this a highly prospective area. ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 9 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU Figure 6: Plan view of the Durack – Windsor area showing previous drilling coloured by maximum down-hole Au (g/t) Mt Pleasant The historic Mt Pleasant pit is located approximately 2km southeast of Five Ways. There is no historic estimate for this area. Mineralisation throughout the bulk of the orebody is interpreted as forming in broad, flat-lying veins striking towards 325º. Extensional RC drilling to the north of the pit has located consistent mineralisation. There are two typical zones for mineralisation, a deeper, more consistent zone at 70m depth which could be related to a deepening of the graphitic schist and another at 25-30m within the oxidation zone. There is excellent potential for a cutback to the north of the Mt Pleasant pit, with the bulk of known gold mineralisation located in this area. Mineralisation remains open to the north in several areas. ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 10 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU Figure 7: Plan view of the Mt Pleasant area showing previous drilling coloured by maximum down-hole Au (g/t) Growth Potential The Company considers Peak Hill to be an extremely prospective area for gold exploration on the basis of previous drilling results, the area’s rich mining history and the fact that it has remained relatively under- explored since mining was last active during a much lower gold price. In addition to the opportunity to extend known mineralisation, recent RC drilling completed by Westgold Resources in 2025 returned several standout intersections which demonstrate highly prospective brownfields potential outside the current estimates. Highlights from drilling around historic workings in the Treasure area, which includes the Treasure, Golden Treasure, Emerald and several other historic underground workings, include: • 19m @ 13.34g/t Au from 104m, including 7m @ 34.57g/t Au from 107m in 25PKRC030 • 10m @ 18.79g/t Au from 19m, including 1m @ 114.25g/t Au from 23m in 25PKRC022 • 4m @ 10.38g/t Au from 48m in 25PKRC022 • 2m @ 19.73g/t Au from 75m, including 1m @ 38.10g/t Au from 75m in 25PKRC032 • 2m @ 38.17g/t Au from 55m, including 1m @ 75.00g/t Au from 55m in 25PKRC033 ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 11 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU • 3m @ 25.04g/t Au from 65m in 25PKRC062 • 5m @ 5.32g/t Au from 79m, including 2m @ 12.30g/t Au from 79m in 25PKRC070. Drilling program details and JORC Table 1 information can be found in Annexure A below. Multi-Rig Programmes to Unlock Growth Potential Great Boulder is currently planning an exploration campaign designed to validate, infill and extend the current mineralisation estimates at Peak Hill for the purposes of completing a Mineral Resource Estimate update. This program, which is planned to include Jubilee, Five Ways, Harmony, Enigma, Durack, Mt Pleasant and the Treasure area, will include up to 40,000m of RC, diamond and AC drilling over the next six months. The key priorities for the initial exploration campaign will be: • Infilling historic estimates and twinning historic holes with RC drilling to validate previous drilling, confirm mineralised zones and provide additional lithology and weathering information • Drilling a limited number of diamond holes for structural orientations, bulk density sampling and potential metallurgical samples • Step-out drilling to test extensional opportunities along strike and/or at depth • Updating geological, structural and mineralisation models • Preparing updated Mineral Resource Estimates for all deposits. Exploration Target Great Boulder has estimated an Exploration Target for the Peak Hill Gold Project which is based upon conceptual extensions of existing mineralisation from geological models, geological mapping, AC, RC and Diamond drilling completed by previous owners and 3D modelling using Micromine software. This Exploration Target is exclusive of the current Mineral Resource Estimate and does not include exploration upside at other known targets within the project area. Explanatory information pertaining to the target range, methodology and planned activities for testing each prospect area is detailed in Annexure A below. TABLE 2: PEAK HILL GOLD PROJECT – GLOBAL EXPLORATION TARGET Tonnes (kt) Grade (g/t Au) Ounces (koz) Lower Upper Lower Upper Lower Upper 18,410 21,340 1.0 1.1 600 740 Tonnages are rounded to 100kt; ounces rounded to 1koz. Rounding errors may occur. The potential quantity and grade of the Exploration Target is conceptual in nature and, as such, there has been insufficient exploration drilling conducted to estimate a Mineral Resource. At this stage it is uncertain if further exploration drilling will result in the estimation of a Mineral Resource. The Exploration Target has been prepared in accordance with the JORC Code (2012). The Exploration Target has been prepared by Great Boulder without any involvement from Westgold or any of its related bodies corporate or any of its/their directors, officers or employees and, as such, none of them assume any responsibility for, or makes any representation or warranty, express or implied, with respect to the accuracy, reliability or completeness of the Exploration Target. ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 12 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU Acquisition Terms Great Boulder has agreed to acquire the Peak Hill Gold Project ("Acquisition") for total consideration made up of a mixture of deposit, cash consideration and consideration shares as follows: • deposit of $1 million (‘’Deposit’’) which has been paid out of existing cash reserves; • cash consideration of $25 million less the Deposit (“Cash Consideration”); • 391.7 million fully paid ordinary shares in Great Boulder (‘’Consideration Shares’’) issued to Westgold such that Westgold will hold 19.9% of the shares on issue in Great Boulder post the Transaction completion and post Placement completion; and • a NSR royalty interest of 1% on the production of gold from the Project tenements (‘’Royalty’’). The Peak Hill Gold Project comprises exploration licence E52/2471, miscellaneous licences L52/2, L52/19, L52/20, L52/39, L52/62, L52/63 and L52/173 and mining leases M52/35, M52/56, M52/297, M52/474, M52/801, M52/1073 and M52/1090 located approximately 100km north of Meekatharra, Western Australia and the Company’s Side Well Gold Project (Tenements). Mining leases M52/35, M52/56, M52/297 and M52/474 and miscellaneous licences L52/2, L52/19, L52/20, L52/39, L52/62, L52/63 and L52/173 are held by Aragon Resources (100%). Aragon Resources is a wholly owned subsidiary of Westgold Resources Limited. E52/2471, M52/1073 and M52/1090 are held jointly by Aragon Resources (85%) and Walter Scott Wilson (15%). M52/801 is held jointly by Aragon Resources (85%) and Horseshoe Gold Mine Pty Ltd (15%). Great Boulder and Aragon Resources have entered into an asset sale and purchase agreement for the sale and purchase of the Project assets (comprising the Tenements including all ore stockpiles, contracts, licences and mining information), a share subscription agreement for the subscription and issue of the Consideration Shares to Westgold, a water licence and access agreement and a royalty deed for the grant and payment of a royalty to Westgold. Completion of the agreements are subject to the following conditions: • Great Boulder completing a capital raising of at least $30 million (before costs) pursuant to the Placement. There are two tranches to the placement with Tranche 2 subject to shareholder approval at a General Meeting indicatively expected to occur in mid-June 2026; • Consent of the Minister to transfer of Aragon Resources’ interest in the Tenements to Great Boulder at completion (to the extent that Ministerial consent is required under the Mining Act); • ASX in-principle advice remaining that no Great Boulder shareholder approval is required under Listing Rules 11.1.2 and 11.1.3 for the Transaction; • All third-party approvals and consents necessary to give effect to the transfer of the Project assets and the transactions contemplated by the Transaction Agreements; and • Great Boulder obtaining shareholder approval required by Listing Rule 7.1 for the issue of the Consideration Shares and the issue of approximately 325.1 million Shares under the Tranche 2 of the Placement. Aragon Resources will be granted a net smelter royalty (NSR) of 1.0% on the production of gold from the Tenements (Royalty). Payment of the Royalty will be secured by the grant of a mining mortgage over the Tenements. Under the terms of the subscription agreement for the issue of the Consideration Shares, Westgold will have the right, but not the obligation, to appoint one person as a non-executive director to the Great Boulder ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 13 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU Board; the Board nomination right will continue until such time that Westgold’s voting interest in Great Boulder is less than 10% for two consecutive months. Great Boulder will also provide Westgold with a right to participate in future issues of shares for cash consideration (subject to customary exceptions, such as issues pursuant to employee incentive schemes or on exercise of convertible securities) so as to provide Westgold with an opportunity to participate in such equity capital raisings in a manner which allows Westgold to maintain its existing percentage shareholding interest in Great Boulder; the participation right will continue until such time that Westgold’s voting interest is less than 10% for two consecutive months. Ore Purchase Agreement The Company has entered into an Ore Purchase Agreement (OPA) with Westgold’s subsidiaries Big Bell Gold Operations Pty Ltd (BBGO) and Aragon Resources Pty Ltd (Mill Owners) for the sale and delivery of gold ore from the Peak Hill Project (Ore) to the Bluebird Mill, Tuckabianna Mill and the Fortnum Mill (each a Mill), being Westgold’s three mills in the region. The key material terms of the Ore Purchase Agreement are summarised as follows: Key term Summary Term and commencement Delivery of the first parcel of ore under the OPA is to occur within 18 months of completing the Acquisition, or such later date as the Parties agree in writing. Ore tonnages The minimum and maximum monthly ore tonnages that the Mill Owners may take during an agreed ore delivery period are: Relevant Mill Minimum Maximum Fortnum Mill 10,000 22,000 Bluebird Mill 20,000 60,000 Tuckabianna Mill 10,000 22,000 Monthly maximum tonnages may be increased by mutual agreement subject to mill availability. The Mill Owner may terminate the agreement if GBR does not deliver the monthly minimum tonnages during an agreed ore delivery period. Ore specifications Minimum grade of 1.0 g/t Au (open pit); 2.5 g/t Au (underground). Deleterious elements to be kept below specified limits. The recoverable gold content of each parcel of ore delivered under the OPA will be agreed by both parties prior to delivery: • average grade will be determined using a conveyor belt sampling mechanism to take representative samples of each parcel material crushed at -28mm (p80 28mm); • grade control samples will be tested for metallurgical recovery; and • Parcel tonnages will be weighed on site and during truck loading prior to delivery. Pricing and payment Mill Owners to pay GBR for Ore delivered on the following basis: ASX ANNOUNCEMENT 4 May 2026 ASX Code: GBR Level 1, 51 Colin St West Perth WA 6005 14 ABN 70 611 695 955 +61 8 9321 6037 Contact: Andrew Paterson, Managing Director admin@greatboulder.com.au GREATBOULDER.COM.AU Payment = Aggregate Gold Payment – Mill Owner’s Costs – Mill Owner’s Margin - State Royalty The Aggregate Gold Payment means the aggregate of the Gold Payments due for each certified Ore parcel delivered in a relevant month (Parcel) where, for each Parcel. Gold Payment means the agreed recoverable gold content in the Parcel x Average Gold Price. Costs terms Mill Owner’s costs means the Certification Costs plus the Processing Costs plus an capital recovery charge of 15% of the processing costs. Certification Costs means the Mill Owner’s costs associated with certifying the tonnes, grade and metallurgical recovery on site prior to delivery. The Average Processing Cost is the average processing cost per tonne during the immediate prior month (but at a minimum will be $30/dry tonne and at a maximum of $50/dry tonne). An additional processing charge may apply for open pit ore applied to the Average Processing Cost, dependent on the gold grade and delivery year for Parcels delivered. The Mill Owner’s Margin is the margin charged by the Mill Owner at varying percentage rates on the difference between the MO Costs and the Aggregate Gold Payment for a relevant month. The margin rate is dependent on the Average Gold Price for the relevant month (in the case of open pit Ore) and the certified gold grade of Parcels (in case the underground Ore). State Royalty is the royalty payable to the State of WA on minerals produced from the Tenements under the Mining Regulations 1981 (WA). Delivery GBR is responsible for the delivery of Ore to the relevant Mill and the costs of delivery and unloading. Termination The OPA may be terminated by a party on 12 months’ notice to the other parties or by mutual agreement. Strategic Collaboration Great Boulder and Westgold have entered a Non-Binding Strategic Collaboration. Over the next 24 months Great Boulder and Westgold (WGX) will work together to evaluate options to fast-track the Side Well Gold Project. The parties will work towards: • delivering more ounces sooner given the proximity of Side Well to WGX’s Infrastructure; • increasing net cashflows from operations; • supporting WGX Infrastructure expansion plans at WGX’s Bluebird site; • operational cost efficiencies; • stronger envir