REG - Greatland Resources - December 2025 O'Callaghans Mineral Resource Stmt.
30/03/2026 07:00
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RNS Number : 5962Y Greatland Resources Limited 30 March 2026
Greatland Resources Limited
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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 (WO(3)) / 0.30% Cu / 0.57% Zn
/ 0.28% Pb for 246Kt WO(3) / 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 (mailto: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 (WO(3)) Copper Zinc Lead
Mt Grade Metal Grade Metal Grade Metal Grade Metal
% kt % kt % kt % 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
Notes:
Mineral Resources are reported as at 31 December 2025, grades are reported to
two decimal places to reflect appropriate precision in the estimate, and this
may cause apparent discrepancies in totals. Cutoffs for the O'Callaghans MRE
are applied based on a NSR using metal prices of US$25.74 lb W (equivalent
to ~US$450/MTU APT), US$4.54 lb Cu, US$1.27 lb Zn and US$0.93 lb Pb.
O'Callaghans is one of the largest high grade tungsten deposits globally.
Figure 2 below illustrates the deposit's positioning relative to other
tungsten resources outside of China, Russia and North Korea.
Importantly, O'Callaghans also benefits from significant grades of recoverable
copper (0.30%), zinc (0.67%) and lead (0.28%) (not included in Figure 2 which
shows tungsten only).
Figure 2: Benchmarking of O'Callaghans MRE against global (ex-China, Russia
and North Korea) tungsten deposits
Notes: Based on publicly available resource information - may not be an
exhaustive list. Refer to the Appendix for associated sources. Resources are
reported in accordance with JORC (2012) or NI 43-101. See the Appendix section
for comparison data sources.
Additional Information on the O'Callaghans Mineral Resource Estimate
O'Callaghans
The O'Callaghans deposit is 100% owned by Greatland Resource Ltd and located
10km south of Greatland's Telfer gold-copper mine (Figure 1), in the Paterson
Province of the East Pilbara region in Western Australia, approximately 485 km
by road south-east of Port Hedland. The O'Callaghans Mineral Resource is
located within an approved mining lease, M45/203.
Geology
The O'Callaghans deposit lies at the contact between the Proterozoic
Puntapunta Formation and the O'Callaghans granite. The Puntapunta Formation
conformably underlies the Wilki Quartzite and overlies the Telfer Formation,
and is described as an outer carbonate shelf deposit consisting of
well-bedded, clastic dolomite and limestone, with lesser amounts of calcareous
sandstone and siltstone. The O'Callaghans granite has been identified at
around 350 m below surface with drilling having defined a zone of
poly-metallic skarn mineralisation up to 60m thick above the granite limestone
contact. The O'Callaghans suite is directly associated with complex skarn
zones, including pyrite-pyrrotite-magnetite skarns with a strong magnetic
expression.
Figure 3: Schematic geological section of O'Callaghans deposit
Mineralisation
Mineralisation containing potentially economic quantities of tungsten, copper,
zinc and lead has been identified approximately 300m below surface as a
sub-horizontal layer of poly-metallic skarn (altered limestone) mineralisation
up to 60m thick on the contact between a large granitic intrusion and
overlying limestones (Figure 3). Tungsten-bearing minerals include both
scheelite and wolframite. Molybdenum and silver are present but are not
currently considered economically significant.
Drilling Overview
Exploration during the 1980s-1990s at O'Callaghans targeted skarn
mineralisation associated with a geophysically interpreted granitoid. Reverse
circulation (RC) drilling conducted across the project area during the
1980s-1990s tested multiple anomalies; however, most holes were insufficiently
deep to intersect the skarn system. In 1985, seven diamond drillholes were
completed to test discrete magnetic anomalies. Six holes intersected
polymetallic skarn mineralisation, confirming a zoned system located
approximately 300 m below surface.
The majority of drilling that informs this MRE was carried out between
2008-2010, including 19 diamond holes in 2008 and 157 diamond holes in
2009-2010, infilling the main mineralised zone to approximately 100m spacing.
Sampling Practices
Most data informing the mineral resource is from 2008-2010 drilling. Sample
preparation was undertaken at Telfer (2008) and in Perth laboratories
(2009-2010). Sample intervals ranged from 0.2m-1.0m. RC samples were collected
at 1m intervals and split using riffle or rotary splitters, producing 2-5kg
primary samples, with bulk rejects retained for reference. Diamond drilling
(DD) sampling followed strict protocols, using geological boundaries, with
half-core samples collected.
Both RC and DD samples were crushed (to ~2 mm), split, and pulverised (~75
µm) prior to assay, using protocols appropriate for the mineralisation.
Quality control included ~5% field duplicates for RC and coarse duplicates for
DD. No second half-core assays were conducted to preserve material for
metallurgical test work.
Geological Interpretation
The O'Callaghans deposit is a polymetallic skarn located at the contact
between limestone of the Puntapunta Formation and an intrusive granite. The
Main Skarn comprises calc-silicate rocks with >10% sulphides, typically
surrounded by a halo containing <10% sulphides. Geological interpretation
was completed for lithology, structure, oxidation, and Pb/Zn metal zonation,
based on drilling data. Lithological domains were treated as hard boundaries,
with domains defined from both logging and assay data.
Structure and oxidation domains were modelled but have minimal impact on the
resource estimate. Final estimation domains align with the geological
interpretation, except for the refined Pb and Zn zonation. The deposit is
characterised as a flat, disc-shaped orebody.
Mineral Resource Estimation
Drillhole data were composited to 2m lengths, with top-cuts applied to Pb/Zn
domains and Mo based on statistical analysis, while all geological and grade
domains treated as hard boundaries. Grade estimation was completed using
ordinary kriging for W, Cu, Zn and Pb and reported for Mineral Resources.
The Mineral Resource is reported through the use of a A$92 net-smelter-return
(NSR) using metal prices of US$25.74/lb W (equivalent to ~US$450/MTU APT),
US$4.54/lb Cu, US$1.27/lb Zn, and US$0.93/lb Pb and cost estimates based on a
combination of the 2014 PFS physicals, current unit rates at nearby Telfer
Mine and escalation from the 2014 PFS where current values were not available.
The Mineral Resource has been classified as Indicated where adequate drilling
density exists (100m × 100m spacing) to demonstrate both geological and grade
continuity within the main mineralised horizon. Inferred Resources form a
peripheral halo to the Indicated category, where drill spacing widens from
100m to 200m. In these areas, geological continuity is established, but
confidence in grade continuity is lower due to increased spacing.
Mineral Resource classification is also constrained by a mine stope-optimised
solid derived using a A$92 NSR cut-off. This approach ensures that the
classification is limited to material within a realistic and potentially
mineable stope geometry.
Mining and Metallurgical Assumptions
A Pre-Feasibility Study (PFS) was completed by previous owner Newcrest Mining
Limited in 2014 that identified long-hole open stoping as the preferred mining
method with decline truck haulage identified as the most suitable to deliver a
2.0Mtpa operation. The proposed processing route involves sequential flotation
(copper, lead, zinc, and pyrite), followed by magnetic separation and gravity
recovery of tungsten concentrate, through a new onsite processing facility.
The PFS contemplated an APT plant to convert tungsten concentrate into high
purity APT.
Metallurgical domains are based on the skarn geology, with subdivision into
lead-zinc rich and lead-zinc poor zones. Metallurgical test work has been
completed on representative samples from both domains with the following
recovery assumptions used for NSR calculation: W 70%, Cu 82.4%, Zn 76.2% and
Pb 70.4%.
Comparison to Previous Mineral Resources
The O'Callaghans Mineral Resources has previously been reported as a Mineral
Resource by both Newcrest Mining Limited and then Newmont Corporation between
2010 and 2023. It was not included by Greatland in its December 2024 MRE as a
technical evaluation was ongoing at that time. With this work now complete it
is the view of the Competent Person that the underlying data and relevant
estimation support Greatland reporting a Mineral Resource estimate for the
O'Callaghan deposit.
Figure 4 provides a comparison between previous reported Mineral Resources for
the O'Callaghans Deposit.
Figure 4: Comparison with previous Mineral Resource estimates
.
Forward Looking Statements
This document includes forward looking statements and forward looking
information within the meaning of securities laws of applicable jurisdictions.
Forward looking statements can generally be identified by the use of words
such as "may", "will", "expect", "intend", "plan", "estimate", "anticipate",
"believe", "continue", "objectives", "targets", "outlook" and "guidance", or
other similar words and may include, without limitation, statements regarding
estimated reserves and resources, certain plans, strategies, aspirations and
objectives of management, anticipated production, study or construction dates,
expected costs, cash flow or production outputs and anticipated productive
lives of projects and mines.
These forward looking statements involve known and unknown risks,
uncertainties and other factors that may cause actual results, performance and
achievements or industry results to differ materially from any future results,
performance or achievements, or industry results, expressed or implied by
these forward-looking statements. Relevant factors may include, but are not
limited to, changes in commodity prices, foreign exchange fluctuations and
general economic conditions, increased costs and demand for production inputs,
the speculative nature of exploration and project development, including the
risks of obtaining necessary licences and permits and diminishing quantities
or grades of reserves, political and social risks, changes to the regulatory
framework within which Greatland operates or may in the future operate,
environmental conditions including extreme weather conditions, recruitment and
retention of personnel, industrial relations issues and litigation.
Forward looking statements are based on assumptions as to the financial,
market, regulatory and other relevant environments that will exist and affect
Greatland's business and operations in the future. Greatland does not give any
assurance that the assumptions will prove to be correct. There may be other
factors that could cause actual results or events not to be as anticipated,
and many events are beyond the reasonable control of Greatland. Forward
looking statements in this document speak only at the date of issue. Greatland
does not undertake any obligation to update or revise any of the forward
looking statements or to advise of any change in assumptions on which any such
statement is based.
Competent Person Statement
The information in this announcement pertaining to estimation and reporting of
the Mineral Resource estimates is based on, and fairly reflects, information
and supporting documentation compiled under the supervision of Michael
Thomson, Principal Geologist at Greatland. Mr Thomson is a full-time employee
of the Greatland Group and has a financial interest in the Company. Mr Thomson
is a member of the Australian Institute of Geology (AIG) and has over 20
years' relevant industry experience. Mr Thomson has sufficient experience that
is relevant to the style of mineralisation and type of deposits under
consideration and to the activity currently being undertaken to qualify as a
Competent Person as defined in the 2012 Edition of the 'Australasian Code for
Reporting Exploration Results, Mineral Resources and Ore Reserves'. Mr Thomson
consents to the inclusion in this announcement of the matters based on that
information and supporting documentation in the form and context in which it
appears.
Independent consulting group SRK Consulting (Australasia) Pty Ltd (SRK) has
reviewed the O'Callaghans Mineral Resource and is of the opinion that the
supporting geological dataset and the geological and estimation methodologies
used to the produce the Mineral Resource Estimate are reasonable and
appropriate for the style of mineralisation of the deposit. Further, SRK
considers that the Mineral Resources have been classified and reported in
accordance with the guidelines and principals outlined in the 2012 edition of
the Australasian Code for the Reporting of Exploration Results, Mineral
Resources and Ore Reserves (JORC Code, 2012 edition).
Appendix 1: JORC Tables
JORC Code, 2012 Edition - Table 1 Section 1: Sampling Techniques and Data
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 44(o) 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.
JORC Code, 2012 Edition - Table 1 Section 2: Reporting of Exploration Results
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.
JORC Code, 2012 Edition - Table 1 Section 3: Estimation and Reporting of
Mineral Resources
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.
Appendix 2: Tungsten Mineral Resource Estimate Benchmarking
Project Ownership Tonnage Grade Contained Metal Link
(kt WO(3))
(Mt) WO(3) %)
Hemerdon Tungsten West 327 0.12% 409 Link
(https://www.londonstockexchange.com/news-article/TUN/development-and-economic-plan-for-hemerdon/17061075)
Northern Dancer Largo 425 0.10% 405 Link (https://minedocs.com/12/Northern_Dancer_2011_PEA.pdf)
Mactung Fireweed Metals 54 0.70% 374 Link (https://fireweedmetals.com/mactung-project/)
Sisson Northcliff Resources 574 0.06% 353 Link
(https://iaac-aeic.gc.ca/050/documents_staticpost/63169/93967/Sisson_43-101_Technical_Report_Final_Mar13.pdf)
Mt Mulgine Tungsten Mining 259 0.11% 285 Link
(https://www.tungstenmining.com/wp-content/uploads/2025/09/250926_Annual-Report-2025.pdf)
Sangdong Almonty Industries 59 0.44% 259 Link
(https://almonty.com/wp-content/uploads/2025/09/Sangdong_NI43_JORC_Tech_Rep_March25_v3.pdf)
O'Callaghans Greatland Resources 70 0.35% 246 Per this announcement
Nui Phao Masan High Tech Materials 97 0.18% 179 Link
(https://www.itia.info/assets/files/25AGM/9_Update_on_Nui_Phao_in_North_Vietnam_Dominic_Heaton_Masan_Resources.pdf)
Dolphin Group 6 Metals 11 0.91% 103 Link (https://wcsecure.weblink.com.au/pdf/G6M/03001623.pdf)
Mt Carbine EQ Resources 41 0.23% 94 Link
(https://www.eqresources.com.au/site/pdf/c8974e48-c7ce-4ee1-95bb-47673d2557eb/Investor-Presentation-Euroz-Hartleys-Conference.pdf?Platform=ListPage)
Watershed Tungsten Mining 49 0.14% 70 Link
(https://www.tungstenmining.com/wp-content/uploads/2025/09/250926_Annual-Report-2025.pdf)
Panasqueira Almonty Industries 15 0.23% 34 Link
(https://almonty.com/wp-content/uploads/2024/05/Panasqueira_43-101_Tech_Rep_Dec16_SEDAR.pdf)
Barruecopardo EQ Resources 21 0.19% 41 Link
(https://www.eqresources.com.au/site/pdf/c8974e48-c7ce-4ee1-95bb-47673d2557eb/Investor-Presentation-Euroz-Hartleys-Conference.pdf?Platform=ListPage)
Pilot Mountain Guardian Metal 13 0.27% 34 Link (https://www.guardianmetalresources.com/project/pilot-mountain-project/)
Gentung Browns Almonty Industries 8 0.32% 24 Link (https://almonty.com/wp-content/uploads/2025/11/Lentung-43-101.pdf)
Hatches Creek Tungsten Mining 12 0.17% 21 Link
(https://www.tungstenmining.com/wp-content/uploads/2025/10/251006_Mineral-Resource-Estimate.pdf)
Valtreixal Almonty Industries 18 0.11% 19 Link
(https://almonty.com/wp-content/uploads/2024/05/Amended_Valtreixal_43-101_Tech_Rep_Oct15_V4.pdf)
Santa Comba Pivotal Metals 10 0.16% 16 Link
(https://cdn-api.markitdigital.com/apiman-gateway/ASX/asx-research/1.0/file/2924-02533050-6A1096215?access_token=83ff96335c2d45a094df02a206a39ff4)
Molyhill Tivan 5 0.26% 12 Link (https://tivan.com.au/project/molyhil/)
Los Santos Almonty Industries 4 0.27% 11 Link
(https://almonty.com/wp-content/uploads/2024/05/Amended_Los_Santos_43-101_Tech_Rep_Oct15_V5.pdf)
Springer Private Group 2 0.48% 10 Link (https://www.silverpredator.com/springer-mine.html)
Grey River Playfair Mining 1 0.73% 9 Link (https://playfairmining.com/projects/grey-river-project/overview/)
Wolfram Camp EQ Resources 3 0.28% 8 Link
(https://www.eqresources.com.au/site/pdf/c8974e48-c7ce-4ee1-95bb-47673d2557eb/Investor-Presentation-Euroz-Hartleys-Conference.pdf?Platform=ListPage)
Currais Novos Largo 4 0.11% 5 Link
(https://www.proactiveinvestors.com/companies/news/75380/largo-announces-pea-for-currais-novos-tungsten-project-in-brazil-163-irr-152m-npv-10860.html)
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