Greatland Resources - December 2025 O'Callaghans Mineral Resource Stmt.
30/03/2026 07:00
RNS Number : 5962Y Greatland Resources Limited 30 March 2026 Greatland Resources Limited E: info@greatland.com.au W: https://greatland.com.au : x.com/greatlandgold NEWS RELEASE | 30 March 2026 December 2025 O'Callaghans Mineral Resource Statement THIS ANNOUNCEMENT CONTAINS INSIDE INFORMATION AS STIPULATED UNDER THE UK MARKET ABUSE REGULATIONS. ON PUBLICATION OF THIS ANNOUNCEMENT VIA A REGULATORY INFORMATION SERVICE, THIS INFORMATION IS CONSIDERED TO BE IN THE PUBLIC DOMAIN. O'Callaghans - A globally significant Tungsten Resource Mineral Resource Estimate for high grade 70Mt Tungsten-Copper-Lead-Zinc deposit Greatland Resources Limited (Greatland or Company) (AIM:GGP, ASX:GGP) is pleased to provide a Mineral Resource Estimate (MRE) for the O'Callaghans tungsten-copper-zinc-lead deposit (O'Callaghans) as at 31 December 2025. O'Callaghans was previously reported as a Mineral Resource & Ore Reserve prior to Greatland ownership. O'Callaghans is one of the largest high-grade tungsten deposits globally and benefits from significant copper, zinc and lead mineralisation. O'Callaghans is 100% owned by Greatland and located just 10km south of Telfer on a mining lease (M45/203) (Figure 1). Key highlights: § Greatland MRE: 70Mt @ 0.35% tungsten trioxide (WO3) / 0.30% Cu / 0.57% Zn / 0.28% Pb for 246Kt WO3 / 207Kt Cu / 371Kt Zn / 182Kt Pb. § Globally significant strategic asset: O'Callaghans is one of the largest high-grade tungsten deposits globally (Figure 2). Tungsten is designated as a critical mineral by many countries including Australia, the United States, the European Union, Canada, the United Kingdom, Japan and India. - Tungsten's extreme melting point, hardness and density make it ideal and difficult to substitute for various applications including in mining, construction, automotive, aerospace, defence, industrial and chemical. Aerospace and defence applications currently account for ~25% of global tungsten demand. China currently produces ~80% of global tungsten supply but imposed export controls on tungsten in early 2025. Historically a net exporter of tungsten, China became a very significant net importer of tungsten in 2025. - These and other geopolitical factors have contributed to a ~500% increase in benchmark pricing for Ammonium Para Tungstate (APT), a high purity tungsten compound, since February 2025, to ~US$2,200 per metric tonne unit (MTU; 1 MTU = 10kg). The O'Callaghans MRE uses pricing of US$450/MTU APT. § Work to date: O'Callaghans benefits from significant drilling and study work completed by previous owners. - The MRE is considered well informed with 71,000m of drilling from 184 drill holes (100m x 100m spacing) supporting the predominantly (>95%) higher confidence Indicated Mineral Resource. - Newcrest Mining Limited (Newcrest) historically reported an O'Callaghans Ore Reserve as recently as 2020, that was supported by a Newcrest 2014 Pre-Feasibility Study (PFS) that demonstrated a technically and economically viable long life mining operation. The PFS contemplated a long-hole open stoping with paste fill, utilising truck haulage and a standalone 2.0Mpta processing facility and APT plant. - The PFS processing flowsheet was sequential flotation (copper, lead, zinc, and pyrite), followed by magnetic separation and gravity recovery of tungsten concentrate. The PFS contemplated an APT plant to convert tungsten concentrate into high purity APT. Metallurgical test work was completed as part of the PFS and is the basis for the MRE net smelter return (NSR) recovery assumptions of: W 70%, Cu 82.4%, Zn 76.2% and Pb 70.4%. § Infrastructure: O'Callaghans is strategically located just 10km south of Greatland's Telfer mine, with synergy potential from the sharing of Telfer's significant existing non-processing infrastructure. Greatland Managing Director, Shaun Day, commented: "O'Callaghans is a globally significant tungsten and base metals deposit that presents latent value and optionality within Greatland's portfolio, particularly in the strong prevailing tungsten market conditions. "Greatland's first Mineral Resource Estimate for the deposit delineates a high grade 70 million tonne resource, the vast majority in the high confidence Indicated Resource category, providing a clearer basis to understand the scale and quality of this strategic asset. "O'Callaghans is one of the world's largest high grade tungsten deposits, in close proximity to our Telfer mine which provides the potential to benefit from sharing of some of Telfer's non-processing infrastructure. While our primary focus will remain Telfer and Havieron, we are considering appropriate options to demonstrate and enhance the project's value within the Greatland portfolio." Contact For further information, please contact: Greatland Resources Limited Shaun Day, Managing Director | Andrew Bowler, Head of Investor Relations info@greatland.com.au Nominated Advisor SPARK Advisory Partners Andrew Emmott / James Keeshan / Neil Baldwin | +44 203 368 3550 Corporate Brokers Canaccord Genuity | James Asensio / George Grainger | +44 207 523 8000 RBC Capital Markets | James Agnew / Jamil Miah | Scott Redwood | +44 207 029 0528 Media Relations Australia - Fivemark Partners | Michael Vaughan | +61 422 602 720 About Greatland Greatland is a gold and copper mining company listed on the Australian Securities Exchange and London Stock Exchange's AIM Market (ASX:GGP and AIM:GGP) and operates its business from Western Australia. The Greatland portfolio includes the 100% owned Telfer mine, the adjacent 100% owned brownfield world-class Havieron gold-copper development project, and a significant exploration portfolio within the surrounding region. The combination of Telfer and Havieron provides for a substantial and long life gold-copper operation in the Paterson Province in the East Pilbara region of Western Australia. 2025 O'Callaghans Mineral Resource O'Callaghans is located 10km south of Telfer on mining lease M45/203 (Figure 1), in the Paterson Province of the East Pilbara region in Western Australia, approximately 485 km by road south-east of Port Hedland. Figure 1: Satellite image showing Telfer mine and infrastructure and O'Callaghans deposit location The O'Callaghans MRE is detailed in Table 1 below. Table 1: 2025 O'Callaghans Mineral Resource Statement
| Classification | Tonnes | Tungsten Trioxide (WO3) | Copper | Zinc | Lead | ||||
| Mt | Grade % | Metal kt | Grade % | Metal kt | Grade % | Metal kt | Grade % | Metal kt | |
| Indicated | 65 | 0.35 | 232 | 0.30 | 195 | 0.58 | 358 | 0.28 | 176 |
| Inferred | 4 | 0.31 | 14 | 0.28 | 12 | 0.39 | 13 | 0.19 | 7 |
| Total | 70 | 0.35 | 246 | 0.30 | 207 | 0.57 | 371 | 0.28 | 182 |
| Criteria | Commentary |
| Sampling techniques | Drilling was undertaken using a combination of reverse circulation (RC) and diamond (DD). Recent programmes have largely used mixed ICP-OES/ICP-MS with aqua regia AAS for gold and silver and ion-specific electrode for fluorine. The significance of tungsten in the mineralisation mandated the use of alkaline peroxide fusion although aqua regia and four-acid digests have also been used. Aqua regia digests may be considered to be strong partial digest; four-acid digests are total for many elements but only near-total for tungsten. Alkaline peroxide fusion is a total digestion technique and is appropriate where wolframite is present. |
| Drilling techniques | The drilling pattern covers about 100 m by 100 m for the highest-grade part of the deposit increasing to a nominal 200 m by 200 m spaced pattern. A small part of the deposit was infilled to a 50 m by 50 m spacing to evaluate short-range grade continuity. The estimate used data from 184 drill holes including wedge holes for a total of 71,700 m drilled. · 7 holes drilled in 1985. · 1 hole drilled in 1991. · 19 holes drilled in 2008. · 157 holes drilled in 2009. |
| Drill sample recovery | Diamond core recovery was systematically recorded in the geological database for 15 holes from the 2008 and 2009 programmes. Core recovery in the mineralised skarn is typically very good. There is likely no impact from core recovery on the Mineral Resource estimate quality. There is no record of RC sample recovery but very little of the recent RC drill samples were analysed and early RC drill holes were pre-collars for diamond drilling, so weren't designed to hit mineralisation. |
| Logging | DD and RC holes were geologically logged for lithology, alteration, mineralisation, veining, vein percentage, and structure. Logging information was recorded and validated prior to merging into the database. All drill core was photographed, either using conventional slide film or a digital camera, prior to cutting the core for sampling. Core from mineralized zones encountered in the 2009 drilling was examined with a high-powered shortwave ultraviolet lamp to estimate scheelite abundance. The fluorescent response of the lamped core was systematically photographed. All diamond holes from 2008-09 programmes have been subject to geotechnical logging. The logging detail is considered appropriate to support the nature of the O'Callaghans mineralisation and suitable for input into resource estimation. |
| Sub-sampling techniques and sample preparation | RC drilling samples were generally collected at 1 m intervals and split using a 1 in 8 riffle splitter or a rotary splitting device attached to the drill rig cyclone. The splitter produced a bulk reject that was bagged (numbered) into plastic bags and stored temporarily for reference and logging. The primary split is between 2 kg to 5 kg. All of the primary assay samples were collected into a calico bag and placed inside the bulk reject plastic bag for identification. DD core sampling follows a detailed protocol to maximize sampling precision. Mineralized and important lithological contacts are used as sample boundaries. Diamond core was cut and half core samples collected. The 2008 and 2009 drilling constitute the vast bulk of the data. Samples from the 2008 program were cut and prepared at Telfer and the pulps shipped to a commercial laboratory in Perth. In the 2009 program full core samples were shipped to Perth in their core trays. Cutting and sample preparation took place on the laboratory's premises. Minimum and maximum sample intervals are 20 cm and 1 m respectively. Diamond core samples are crushed to nominal 95% passing 2 mm and half split collected by rotary sampling device. The entire split is pulverized (nominal 95% passing 75 \u03bcm tested at a rate of 1 in 25) in an LM5 mill. A 250 g assay subsample is taken by a scoop. This protocol is considered appropriate for the mineralisation style. RC samples for assay are crushed to nominal 95% passing 2 mm and split to a maximum of 3 kg, all of which is pulverized in the LM5. This protocol is also considered appropriate for the mineralisation style. Field duplicates of RC drilling were collected at the rate of 5% Coarse duplicates (from the crusher) were taken for diamond core samples, also at the rate of about 5% No second half core analyses were carried out due to the need to preserve as much core as possible for metallurgical test work |
| Quality of assay data and laboratory tests | With very few exceptions, O'Callaghans samples were analysed at independent commercial laboratories. There has been a wide range of elements determined over the life of the prospect. Similarly, a wide variety of analytical methods have been used. Early programs determined most elements by AAS with pressed powder XRF, fire assay, and colorimetry being used where appropriate. Recent programmes have largely used mixed ICP-OES/ICP-MS with aqua regia AAS for gold and silver and ion-specific electrode for fluorine. The significance of tungsten in the mineralisation mandated the use of alkaline peroxide fusion although aqua regia and four-acid digests have also been used. Aqua regia digests may be considered to be strong partial digest; four-acid digests are total for many elements but only near-total for tungsten. Alkaline peroxide fusion is a total digestion technique and is appropriate where wolframite is present. Drilling at O'Callaghans up to 1996 was not supported by QAQC protocols. Drilling programmes in 2008 and 2009 (which make up more than 90% of the diamond drilling) were accompanied by QAQC protocols that included certified reference materials (CRM) including primary tungsten reference materials from Canmet, blanks, second laboratory checks, coarse duplicates, pulp duplicates, and umpire analyses. Accuracy has been monitored through: · CRMs at a submission rate of approximately one in ten. · Laboratory standards at a rate of one in twenty. Tungsten median bias for CRMs above 750 ppm W (including the three primary CRMs) is -1.1%. Copper bias is +0.5% and zinc +1.7%. Lead bias is zero for all data and -0.2 for CRMs above 1000 ppm lead. None of the bias figures suggest any issues. Blank results are generally as expected with the highest reported assays above detection limits for (all these results are less than ten times detection limit). |
| Verification of sampling and assaying | Detailed procedure for data collection and collation which includes hole naming, logging, collection of sample material for assay, receipt of assay results, drill hole collar pickup, downhole survey, and data QAQC. The database has automatic validation checks, with all data validation protocols overseen by centralized database team. The validation process is multi-staged, requiring input from geologists, surveyors, and assay laboratories. Details of sampling were recorded digitally using a handheld barcoding system. All samples recorded as missing were coded and checks carried out for overlaps or gaps in the samples. Internal data quality reviews were conducted by site teams and resource personnel prior to resource estimation. No twin holes have been drilled. There has been no adjustment to assay data. Where re-assay has shown earlier assays to be erroneous both sets of data are stored in the database with a comment to indicate the authority by which the second set has been added. |
| Location of data points | Surface drill rigs are positioned using surveyed collar pegs and lined up using compass lines. The dip of each hole is established using an inclinometer. Drill hole collars were surveyed by mine surveyors on completion of the drill hole. Several different downhole survey methods were utilized at O'Callaghans during previous exploration phases. Most recently, drill holes were downhole surveyed on completion using a Miniature Multi-shot Tool or gyroscopic tool at between 10 m and 30 m intervals. A local mine grid, Telfer Mine Grid 2002, covers the whole of the Telfer mine area. It is oriented with grid north at 44o west of magnetic north. The grid was established with several accurately defined datums. The Telfer region natural surface topography is based on surface surveys (LIDAR) prior to the commencement of mining. |
| Data spacing and distribution | The drilling pattern is approximately 100 m by 100 m for the highest-grade part of the deposit widening to a nominal 200 m by 200 m spaced pattern outside the known high grade. A small part of the deposit was infilled to a 50 m by 50 m spacing to evaluate short-range grade continuity. The estimate used data from 184 drill holes including wedge holes for a total of 71,700 m drilled. |
| Orientation of data in relation to geological structure | Surface drilling is orientated vertically to sub-vertical to ensure optimal intersection angle for the flat-lying mineralisation. Acceptable intersection angles are considered during the drill hole planning process. No orientation bias has been indicated in the drilling data to date. |
| Sample security | The security of samples is controlled by tracking samples from the drill rig to the database. RC samples were collected and barcoded. Barcoding involves attaching plastic tags with a barcode and number to the calico bag. The process was established with a series of checks to ensure that all samples were collected and all appropriate barcodes attached to bags. The barcoded calico bags were collected and delivered to the analytical laboratory. The RC procedure also applied to diamond drill holes in the 2008 programme but in 2009 whole core was freighted to Perth for cutting and preparation at the laboratory. The core was shipped in trays that minimized the relative movement of core pieces. The trays were packed and sealed to be tamper-evident. Any discrepancy between the packing list and the samples delivered was notified immediately to the site. Details of all sample movements are recorded in a database table. Dates, BHID, sample ranges, and the analytical suite requested are recorded with the dispatch of samples to analytical services. Any discrepancies logged at the receipt of samples into the analytical services are validated. Data was entered into the database directly from the laboratory results file, i.e. there was no keying of assay results. |
| Audits or reviews | Internal data quality reviews are conducted by site teams and resource personnel prior to resource estimation. Site personnel carry out laboratory inspections during the 2009 programme sample logging, cutting, and preparation was carried out at the laboratory. An external independent third-party consultancy at regular intervals undertakes a review of the Mineral Resource estimation which includes a review of the input data. This was last completed by SRK Consulting in 2026. |
| Criteria | Commentary |
| Mineral tenement and land tenure status | The O'Callaghans poly-metallic deposit is located approximately 10 km south of Greatland's Telfer Gold Mine in Western Australia within approved mining lease ML45/203. |
| Exploration done by other parties | Geophysical exploration by Newmont Pty Ltd between 1972 and 1983 identified the presence of a granitoid in the O'Callaghans area. A high resolution ground magnetic survey was carried out over several airborne magnetic anomalies during 1984. Seven diamond drill holes were completed in 1985 to test discrete magnetic anomalies for possible skarn mineralisation associated with the granitoid. The drilling, together with deflation lag sampling and mapping, confirmed the presence of a zoned system of poly-metallic skarn mineralisation above the granitoid. A grid of reverse circulation drill holes during the 1980s and 1990s failed to intersect the skarn mineralisation, although one deep drill hole in 1987 to the northwest of the main skarn intersected the granitoid contact. One diamond drill hole was drilled during 1991 that intersected thin skarn mineralisation. 19 diamond drill holes were completed during 2008 to further test the extent of skarn mineralisation and to infill the grid to 200 m in the main mineralized area. During 2009 and 2010, 157 diamond drill holes were completed to infill the grid to 100 m centres over the main mineralisation. |
| Geology | The O'Callaghans deposit is a polymetallic skarn deposit which lies at the contact between the Proterozoic Puntapunta Formation and the O'Callaghans granite. The Puntapunta Formation conformably lies between the Wilki Formation and the Telfer Formation and considered to be outer carbonate shelf deposits consisting of well-bedded, clastic dolomite and limestone, with lesser amounts of calcareous sandstone and siltstone. The O'Callaghans granite was identified at around 350 m below surface based on diamond drilling intercepts and geophysical surveys. Drilling defined a zone of poly-metallic skarn mineralisation up to 60 m thick above the granite/limestone contact. The O'Callaghans granite is variably altered and is not readily grouped with other regional granitic suites. The O'Callaghans granite is directly associated with complex skarn zones, including pyrite/pyrrhotite/magnetite skarns with a strong magnetic expression. It is the only granite known to be associated with extensive hydrothermal alteration systems and metal anomalies (W-Cu-Bi-Mo-Sn-Pb-Zn). Folded Puntapunta Formation sedimentary rocks appear to be overprinted by variable metamorphic alteration. Sulphide mineralisation related to high-temperature metasomatic skarn formation is consistent with a rapid onset of amphibolite facies contact metamorphic alteration of the host rocks (tremolite/hornblende + biotite). This forms an irregular metamorphic contact aureole above the O'Callaghans granite stock and is a valuable visual aid in recognizing onset and distribution of sulphide mineralisation. The skarn mineralisation and metamorphic aureole overlies a massive, sub-horizontal, poorly mineralized, quartz flooded zone, which in turn overlies weakly foliated granite. Contact with the granite is relatively sharp. The Main Skarn is identified as calc-silicate rock containing more than 10% sulphides generally surrounded by a halo of calc-silicates with less than 10% sulphides. Tungsten, copper, zinc and lead are considered potentially economically extractable. However elevated levels of molybdenum and silver are also present. Tungsten-bearing minerals include both scheelite and wolframite. Gold is not present in economically significant amounts. Fluorine levels show some elevated levels and range between 0.29% and 5.69%. Metal zoning is identified within the overall skarn with two areas of elevated zinc and lead broadly associated with a tungsten mineral species change from scheelite to wolframite. |
| Drill hole Information | Not applicable to the mineral resource estimate. |
| Data aggregation methods | Significant assay intercepts are reported using length-weighted averages based on predefined thresholds, with a maximum allowable internal dilution. For mineral resource estimates, data aggregation methods are aligned with sampling, drilling, and recovery techniques. No exploration results are included in this report, as it focuses on Mineral Resources. |
| Relationship between mineralisation widths and intercept lengths | No exploration has been reported in this release, therefore there are no relationships between mineralisation widths and intercept lengths to report. This section is not relevant to this report Mineral Resources. |
| Diagrams | As provided. |
| Balanced reporting | Significant assay intervals represent apparent widths, as drilling is not always perpendicular to the dip of mineralisation. True widths are typically less than downhole widths and can only be estimated once all results are received and final geological interpretations are completed. No exploration results are included in this report, so relationships between mineralisation widths and intercept lengths are not applicable to the Ore Reserves and Mineral Resources report. |
| Other substantive exploration data | Not applicable to the mineral resource estimate. |
| Further work | Further work is planned to evaluate exploration opportunities that extend the known mineralisation and to improve confidence of the model. |
| Criteria | Commentary |
| Database integrity | Data is stored in a SQL Server database known as acQuire. Assay data and geological data are electronically loaded into acQuire. Regular reviews of data quality are conducted by site and corporate teams prior to resource estimation in addition to external reviews. Detailed data review was completed before the estimation of the deposits. Checks included validation of collar surveys against planned locations and downhole surveys consistency of hole path. Assays were reviewed and compared against observed mineralisation. Logging records were reviewed against core photographs as part of the interpretative geology compilation. All corrections were completed before final data extraction for input to the Mineral Resource estimation. |
| Site visits | The Competent Person for Telfer mineral resources regularly visits the site. |
| Geological interpretation | The O'Callaghans deposit is a polymetallic skarn deposit located at the contact between limestone of the Puntapunta Formation and an intrusive granite. The Main Skarn is identified as calc-silicate rock containing more than 10% sulphides generally surrounded by a halo of calc-silicates with less than 10% sulphides. Sectional strings and wireframes were constructed for lithology, oxidation and structure and lead/zinc metal zonation using all available drilling data. Domains are based on the lithological logging of drill holes and on assay grades for the lead/zinc metal zonation domains. All lithological domains were treated as hard boundaries. Metal zoning was identified within the overall skarn with two areas of elevated zinc and lead broadly associated with a tungsten mineral species change from scheelite to wolframite. To address the risk associated with uncontrolled smoothing of high-grade zinc and lead grades, two elevated lead zinc zones were identified and modelled and treated as hard domains within the main skarn. Thereby restricting the interpolation of Zn and Pb to the defined zones. The zones in the original 2011 grade model were updated in 2016. The original zones were considered simplistic and deterministic as they were created by vertical projection only of a visually interpreted contact. The 2016 model used implicit modelling including non-vertical contacts (full 3-dimensional resolution). Structure and oxidation domains were modelled but they have little influence on the resource estimate. The final estimation domains are the same domains which are represented in the geological interpretation with the exception of the Zn and Pb portions. |
| Dimensions | Flat disc-shaped orebody, the Main skarn extends 1.2 x 1km in plan and is up to 60m thick in the centre thinning out towards the flanks, 350m below surface. |
| Estimation and modelling techniques | All drill hole samples were composited to 2 m length. The residual from compositing were retained by rescaling the composite lengths to include them. As such the final composite lengths vary from 1.35 m to 2.4 m in the main skarn domain. Top-cuts were determined based on a review of histograms and log probability plots for the domain composites. Top-cuts were applied to lead / zinc-rich domain, the lead /zinc poor domain and molybdenum. All lithological and grade domains are treated as hard boundaries. Domains were assigned and coded to the drill hole data and blockmodel. Grade estimation was performed using ordinary kriging. The Pb and Zn elements were re-modelled in 2016 in following recommendations from an external review. Estimation was performed for 16 elements: tungsten, copper, zinc, molybdenum, lead, silver, arsenic, gold, bismuth, cadmium, cobalt, fluorine, iron, sulphur, antimony and tin. Not all variables are estimated throughout the entire block model due to insufficient data. Tungsten, copper, zinc and lead only are reported for the Mineral Resource estimation. Block cells of 50 m x 50 m x 5 m in X, Y and Z were used to fill the boundaries of the domains. Sub-cells with a minimum of 10 m x 10 m x 5 m in X, Y and Z. The maximum block model cell size is equal to spacing in the most densely drilled sections and half the average drill spacing. A declustering analysis was conducted for the main elements. The declustering had little impact on the mean grades. A review of top cuts for the composites was conducted to manage risk and restrict the effect of outliers. Top cuts were determined based on a review of histograms and log probability plots for the domain composites. As the contact skarn mineralisation is dome-shaped over the top of the intrusive body, anisotropy search and variogram orientations were applied where each block model cell is assigned a bearing and plunge by Locally Varying Anisotropy (LVA). The initial search ellipse was oriented flat with an isotropic search in the plane for each element. This was then rotated by the applied LVA orientation. The dimensions for the search ellipse for all elements except Pb and Zn were 300 m in the plane of the skarn (x and y) and 40 m vertically. Pb and Zn were internally domained within the skarn horizon requiring customised search volumes ranging typically 200-250m (x & y) and 20-72m (z). A minimum of 9 and a maximum of 16 samples were required to estimate grades for all elements except Pb and Zn where minimum 9 and maximum 20 were applied. Discretisation for all domains was set at 5 by 5 by 5 (X, Y, Z). The wolframite mineral probability was estimated using indicator kriging. Tungsten is reported as part of the Mineral Resource as tungsten trioxide (WO3). The conversion was done by formula WO3=W x 1.2611 The final skarn grade estimates were validated visually against the input drill hole composites. Swath plots comparing model and sample data show an expected (smooth modelled vs. varied sample grades), correlation with no obvious bias. |
| Moisture | All tonnages are calculated and reported on a dry tonne basis. |
| Cut-off parameters | A specific cut-off grade was not used. Each block within the resource model is assigned a value based on an estimate of its net smelter return. Net smelter return is calculated on a payable metal basis taking into account metal prices, metallurgical recoveries, processing costs and realisation costs. Value / profit cut-off includes mining costs, processing costs with assigned sustaining capital and G&A components. The cost of grade cutoff applied to the Mineral Resource (NSR) is A$94. |
| Mining factors or assumptions | A 2014 Pre-feasibility Study was completed in 2014 for the O'Callaghans deposit. Underground mining methods examined were sub-level caving, trough caving, long-hole open stoping, and room and pillar. Long hole open stoping was selected as the optimum mining method due to the shape of the orebody and hydrological conditions. Materials handling options considered included truck, conveyor, shaft, and a combined shaft and haul. Trucking was selected as the optimum materials handling method due to simplicity, scalability, and low capital requirements. A NSR decline truck haulage with no ore sorting at NSR cutoff A$94. |
| Metallurgical factors or assumptions | The proposed process route involves a four-stage copper, lead, zinc, and pyrite sequential flotation, followed by a magnetic separation stage and finally gravity separation of tungstate concentrate. This will be through the current Telfer Mill Facility. The metallurgical domains used to date are based on the pre-defined skarn domain and the separation of the lead-zinc rich and lead-zinc poor domains. Metallurgical test work has been completed on representative samples of both the lead-zinc rich and lead-zinc poor sub-domains. |
| Environmental factors or assumptions | Mining and ore processing operations at Telfer are conducted pursuant to a series of granted environmental and other approvals. |
| Bulk density | Bulk density values were determined from 914 measurements taken from 73 holes for the main geological domains using wet/dry weight calculations. Densities results were averaged for each domain and the average bulk density assigned to the appropriated block model domain. |
| Classification | The Mineral Resource estimate was classified as Indicated Mineral Resource where drill hole data is considered to be sufficient to demonstrate grade and geological continuity within the main mineralized horizon. For Indicated the drill holes are spaced at 100 m x 100 m in X and Y. The Inferred Mineral Resource occurs in a narrow halo around the Indicated Mineral Resource where the drill spacing transitions from 100 m to 200 m spaced holes and where there is enough drill hole data to demonstrate geological continuity but grade uncertainty increases in areas of wider drill hole spacing No metallurgical or geotechnical assumptions are incorporated in the Mineral Resource estimate. Block model cell size is restricted to a mining stope optimisation outline which coincides with mining assumptions for possible extraction long-hole open stoping technique. |
| Audits or reviews. | Multiple independent reviews have been carried out on the O'Callaghans MRE since 2010, with the most recent review completed in 2026 by SRK Consulting. |
| Discussion of relative accuracy/ confidence | For an Indicated Resource it is considered reasonable for the relative uncertainty to be +/- 15% in tonnage, grade, and metal (exclusive of each other, i.e., each variable has to satisfy the for an annual production volume at a 90% confidence level. Geostatistical evaluations of estimated grades indicate that these criteria can be satisfied. Inferred resources reflect the wide-spaced drilling where the Geological evidence is sufficient to imply but not verify geological and grade (or quality) continuity. |
| Project | Ownership | Tonnage (Mt) | Grade WO3 %) | Contained Metal (kt WO3) | Link |
| Hemerdon | Tungsten West | 327 | 0.12% | 409 | Link |
| Northern Dancer | Largo | 425 | 0.10% | 405 | Link |
| Mactung | Fireweed Metals | 54 | 0.70% | 374 | Link |
| Sisson | Northcliff Resources | 574 | 0.06% | 353 | Link |
| Mt Mulgine | Tungsten Mining | 259 | 0.11% | 285 | Link |
| Sangdong | Almonty Industries | 59 | 0.44% | 259 | Link |
| O'Callaghans | Greatland Resources | 70 | 0.35% | 246 | Per this announcement |
| Nui Phao | Masan High Tech Materials | 97 | 0.18% | 179 | Link |
| Dolphin | Group 6 Metals | 11 | 0.91% | 103 | Link |
| Mt Carbine | EQ Resources | 41 | 0.23% | 94 | Link |
| Watershed | Tungsten Mining | 49 | 0.14% | 70 | Link |
| Panasqueira | Almonty Industries | 15 | 0.23% | 34 | Link |
| Barruecopardo | EQ Resources | 21 | 0.19% | 41 | Link |
| Pilot Mountain | Guardian Metal | 13 | 0.27% | 34 | Link |
| Gentung Browns | Almonty Industries | 8 | 0.32% | 24 | Link |
| Hatches Creek | Tungsten Mining | 12 | 0.17% | 21 | Link |
| Valtreixal | Almonty Industries | 18 | 0.11% | 19 | Link |
| Santa Comba | Pivotal Metals | 10 | 0.16% | 16 | Link |
| Molyhill | Tivan | 5 | 0.26% | 12 | Link |
| Los Santos | Almonty Industries | 4 | 0.27% | 11 | Link |
| Springer | Private Group | 2 | 0.48% | 10 | Link |
| Grey River | Playfair Mining | 1 | 0.73% | 9 | Link |
| Wolfram Camp | EQ Resources | 3 | 0.28% | 8 | Link |
| Currais Novos | Largo | 4 | 0.11% | 5 | Link |
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