DEVELOP GLOBAL LIMITED - Regulatory Filings 2023

ASX Announcement 11 October 2023

- Woodlawn Copper Zinc Project, NSW

Woodlawn Resource increases by 40%, paving way for +10-year mine life

Expanded inventory of more than 10Mt will underpin new mine plan in March-24 quarter

Highlights

Highly successful exploration results in a major 40% increase in the Woodlawn Resource to 10.3Mt at 1.8% Cu, 6.1% Zn, 2.2% Pb, 47.2gpt Ag & 0.5gpt Au (4.3% CuEq[1] );
Previous 2022 estimate; 7.3Mt at 5.7% Zn, 1.8% Cu, 2.0% Pb, 44.9gpt Ag & 0.6gpt Au[2]
Significant increase in Resource tonnages and grades has boosted contained metal for Copper by 43% to 190,000t and Zinc by 50% to 620,000t for a combined 445,000t CuEq[1]
Higher geological confidence Measured and Indicated Resources has increased by 48% (2.35Mt) and now accounts for 70% of total Resource tonnage (7.2Mt)
Expanded Resource paves the way for an increase in mine life from 7 years currently to +10 years based on existing processing throughput capacity of 850,000tpa
Increased Resource estimate does not include assays from drilling after June 30, 2023; Numerous assays results remain outstanding
Resource calculated by leading mining and geological consultants Entech
Total Resource estimate is all within 900m from surface; Mineralisation is open down plunge and along strike to the north and south; Multiple new lenses identified
Understanding of the mineral system with this drilling campaign has improved greatly; Resource tonnes added at a cost of just $5/tonne
A further Resource and Reserve update is scheduled for the March Quarter 2024; This will feed into a new mine plan

Develop (ASX: DVP) is pleased to announce a 40 per cent increase in the Resource at its Woodlawn copper and zinc mine in NSW.

The increase, which stems largely from a highly successful exploration and drilling program that has discovered new lenses of mineralisation, means Woodlawn now has substantial scale with outstanding potential for further growth.

Develop Managing Director Bill Beament said: “This is an outstanding result which demonstrates that Woodlawn is well on track to becoming a significant producer of the copper and zinc which will be in huge demand as part of the world’s energy transition.

“This major expansion of the Resource paves the way for an increase in Woodlawn’s mine life from the existing 7 years to 10-plus years based on the existing processing throughput capacity of 850,000tpa.

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“This increased mine life will be a key feature of the new mine plan, which is set for release in the March 2023 quarter”.

Mr Beament said the outstanding results of Develop’s maiden drilling program at Woodlawn following its acquisition in mid-2022 meant the project now has genuine scale with significant scope for further growth.

“With 7.2Mt of the increased Resource now in the higher geological confidence category of Measured and Indicated, we are well on track to increasing the Reserves, mine life and overall returns at Woodlawn,” he said.

“Our focus is now on completing the remaining infill drilling to drive further increases in Resources, Reserves and mine life.

“The organic growth since we acquired Woodlawn has been exceptional. We are adding resources at a cost of just $5 a tonne at what is one of Australia’s highest-grade copper-zinc mines.

“Importantly, the Resource remains open along strike to the north and south and is completely untested downplunge.”

Woodlawn Project

Develop’s Woodlawn Copper-Zinc Mine is in the world-class Lachlan Fold belt in NSW, 250km south-west of Sydney. Historically, the Woodlawn Mine operated from 1978 to 1998 and processed 13.8Mt grading 9.1% Zn, 1.6% Cu, 3.6% Pb, 74gpt Ag and 0.5gpt Au[3] . It was one of Australia’s highest grade base metal mines at the time.

Develop believes that the project has significant growth potential, having historically been under-explored and untested at depth. In particular, Woodlawn has strong potential for extensions of existing lenses which are open at depth and along strike, and for the discovery of additional lenses, with logical structural positions untested.

Resource Details

The updated Woodlawn MRE of 10.3Mt @ 1.8% Cu, 6.1% Zn, 2.2% Pb 47.2gpt Ag & 0.5gpt Au is reported on the basis of a Net Smelter Return (NSR) and represents the most robust resource for the deposit to date including geometallurgical domaining and recoveries and to fully elucidate the potential for economic extraction. The Mineral Resource Estimate has been independently prepared by leading mining and geological consultants Entech.

Two NSR cut-offs were used:

A NSR of $100 was used for mineralisation in unmined (virgin) areas; and
A NSR of $140 was used for previously mined (remnant) areas, which reflects higher associated costs for mining and metal recovery these areas. Minable Stope Optimisation (MSO) shapes were applied to areas of remanent mineralisation.

Classification Tonnes (kt) NSR (A$/t) Cu % Pb % Zn % Ag gpt Au gpt	Classification Tonnes (kt) NSR (A$/t) Cu % Pb % Zn % Ag gpt Au gpt

Measured	1,311 397 2.3 1.6 5.3 48.5 0.9
Indicated	5,918 336 1.9 1.7 4.9 34.6 0.4
Inferred	3,045 478 1.6 3.4 8.7 71 0.5
Total	10,273 386 1.8 2.2 6.1 47.2 0.5

Table 1 Woodlawn Underground Copper-Zinc Mineral Resource

Due to delays in laboratory turn-around times, the updated MRE contains assay results from drilling up to 30 June 2023 which is approximately 60% of drilling completed by Develop to date. Pending results from the already completed drilling, along with the current infill programme are expected to feed into the next MRE update, schedule for completion in the March quarter 2024.

Significantly, 7.2Mt (70%) of the Mineral Resource is now classified within the higher geological confidence category of Measured and Indicated, a 48% increase on the August 2022 estimate, with the remaining resources in the Inferred category (Table 2).

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This significant increase in Measured and Indicated Resource is extremely important for the amount of mineralisation that is available to be converted into the next Reserve estimate due in the March quarter 2024, this Reserve will form the basis for the March quarter 2024 mine plan update.

The Woodlawn mine plan update, released on 12 September 2023 and further amended on 27 September 2023, which had a pre-tax NPV of A$481 million and didn’t include any of these significant Resources additions was based on a 5.1Mt mineral inventory of which the Reserves were 66% or 3.4Mt of the inventory (see ASX announcement titled “Updated Woodlawn mine plan to generate exceptional returns” dated 12 September 2023 and ASX announcement titled “Amended – Updated Woodlawn mine plan” dated 27 September 2023). Hence the substantial increase in Resource and classification of Resource in the October 2023 estimate bodes well for a significant increase in mine life in the March 2024 quarter update. The contained metal has also significantly increased to 190,000t Cu (+43%), 620,000t Zn (+50%) (445,000t CuEq[1] ).

As a part of the MRE update multiple new lenses have also been confirmed, including a very high-grade copper domain along strike of J Lens and an unconstrained stacked set of lenses to the north of the historic deposit boundary.

The high-grade copper domain identified to the south of J Lens is interpreted to represent a reactivated feeder-fault, that has created a continuous domain of thickened high-grade mineralization.

The newly identified (stacked) lenses to the north of Woodlawn have also resulted in significant extensions to the deposit in an area that has not previously been drill-tested. Encouragingly, the lenses are located adjacent to the large (untested) ‘Bucklands' geophysical anomaly that was previously identified by Heron Resources (see ASX announcement released on 7 May 2019).[4]

The lenses remain open along strike and down plunge. A follow-up drilling program is underway and is designed to infill and test for extensions to these newly discovered lenses.

Results from Develop’s extensive drilling program has greatly improved the geological understanding of the mineral system and will aid future targeting and growth programs.

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----- Start of picture text -----

Woodlawn Resource Comparison (Aug-22 to Oct-23)
12
10.3Mt
10 0.6
1.1
3
8 7.3Mt 1.2
6 2.5
5.9
4
4.8
2
0.1 1.3
0
2022 MRE 2023 MRE
Measured Indicated Inferred
MRE tonnes contained (Mt)
----- End of picture text -----

Table 2 - Woodlawn underground Zinc-Copper Mineral Resource comparison 2022 to 2023

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Importantly a further 3.9Mt of remnant mineralisation has been excluded from the MRE due to its proximity to historic workings. Develop will continue to investigate the potential for extraction of this material, and addition into future MRE’s and mine plans.

==> picture [418 x 342] intentionally omitted <==

Figure 1 Woodlawn 2023 MRE block model classification (cross-section North view).

The ~23Mt[3] Woodlawn mineral system is drilled to a maximum depth of only ~900m below surface and remains open at depth and along strike. The deposit is rapidly growing into a geological system of scale (Figure 2).

==> picture [508 x 213] intentionally omitted <==

Figure 2 Woodlawn 23Mt mineral system comparison to other known significant global orebodies

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3. Included past productions related to operational period of the Woodlawn project between 1978 and 1998, and is based on publicly available information reported by Heron Resources and Develop :

8.0Mt @ 8.3% Zn, 1.6% Cu, 3.1% Pb & 62gpt Ag from the Woodlawn open pit (1978-1987);
0.5Mt @ 13.0% Zn, 1.6% Cu 2.2% Pb & 33gpt Ag from the (satellite) Currawang mine (1991-1995);
5.8Mt @ 10.1% Zn, 1.6% Cu, 4.1% Pb, 90gpt Ag & 0.5gpt Au from Woodlawn Underground (1987-1998);
10.3Mt @ 6.1% Zn, 1.8 Cu, 2.2% Pb, 47gpt Ag & 0.5gpt Au Current Underground Mineral Resource (2023).

Roseberry: MMG Stock Exchange of Hong Kong announcement 13 July 2023 ‘Report of exploration results from Las Bambas and Rosebery’ Kidd Creek: Glencore - Canda Website

Golden Grove: 29 Metals ASX announcement 23 February 2023 ‘December 2022 Mineral Resources & Ore Reserves estimates’. Sulphur Springs: Develop ASX Announcement 02 June 2023 ‘ Sulphur Springs Updated Mineral Resource Estimate’.

Woodlawn: Develop ASX announcement 02 August 2022 ‘Woodlawn Updated Mineral Resource Estimate’ and historic production reports.

This announcement is authorised for release by the Board of Directors.

Investor Enquiries Media Enquiries Bill Beament Paul Armstrong Develop Read Corporate T: +61 8 6389 7400 P: +61 8 9388 1474 E: [email protected] E: [email protected]

About Develop

Develop (ASX: DVP) has a twin-pronged strategy for creating value. The first of these centres on the exploration and production of future-facing metals. As part of this, the Company owns the Sulphur Springs zinc-copper-silver project in WA’s Pilbara region. This project is currently the focus of ongoing exploration to grow the inventory and various development studies. Develop also owns the Woodlawn zinc-copper project in NSW. Woodlawn, which is on care and maintenance, comprises an underground mine and a new processing plant. The second plank of Develop’s strategy centres on the provision of underground mining services. As part of this, Develop has an agreement with Bellevue Gold (ASX: BGL) to provide underground mining services at its Bellevue Gold Project in WA.

Woodlawn Mineral Resources Statement

Classification	Tonnes (kt) NSR (A$/t) Cu % Pb % Zn % Ag gpt Au gpt

Measured	1,311 397 2.3 1.6 5.3 48.5 0.9
Indicated	5,918 336 1.9 1.7 4.9 34.6 0.4
Inferred	3,045 478 1.6 3.4 8.7 71 0.5
Total	10,273 386 1.8 2.2 6.1 47.2 0.5

Tonnages are dry metric tonnes. Minor discrepancies may occur due to rounding.

References

1. The copper equivalent grades for Woodlawn (Cu Eq) are based on copper, lead, zinc, silver and gold prices of US$8330t Copper, US$2160/t Lead, US$2315/t Zinc and US$23.5/oz Silver, and US$1926/oz Gold (price deck based on LME spot as 10/10/2023), with metallurgical metal recoveries of 89% Cu, 85% Pb, 92% Zn, 78% Ag and 43% Au respectively based on historical recoveries at Woodlawn and supported by metallurgical test work undertaken. The copper equivalent calculation is as follows: Cu Eq = (Cu grade % * Cu recovery %) + ((Pb grade % * Pb recovery % * (Pb price $/t/Cu price$/t)) + ( Zn grade% * Zn recovery* (Zn price $/t/Cu price$/t)) + (Ag grade g/t /31.103 * Ag recovery % * (Ag price $/oz/Cu price $/t)) + (Au grade g/t /31.103 * Au recovery % * (Au price $/oz/Cu price $/t))

2. The previous (2022) Woodlawn Mineral Resource Estimate has been extracted from the Company’s ASX announcement titled “Woodlawn Updated Mineral Resource Estimate” released on 2 August 2022.

3. The information in this Announcement regarding previous operations at the Woodlawn Project, including information relating to historic production, recoveries, mineral resources and financial information has been sourced using publicly available information and crossreferenced against internal data for confirmation.

4. Historic IP geophysical anomaly at Woodlawn and Bucklands a data from Heron Resource ASX announcement dated 7 May 2019.

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The Company confirms that it is not aware of any new information or data that materially affects the information included in the relevant announcement and all material assumptions and technical parameters underpinning the estimates in the relevant announcement continue to apply and have not materially changed.

Competent Person Statement

The information in this announcement that relates to Exploration Results at the Woodlawn Project is based on information complied or reviewed by Mr Luke Gibson who is an employee of the Company. Mr Gibson is a member of the Australian Institute of Geoscientists and Mr Gibson has sufficient experience with the style of mineralisation and the type of deposit under consideration. Mr Gibson consents to the inclusion in the report of the results reported here and the form and context in which it appears.

The information contained in this announcement relating to the Woodlawn Underground Resources is based on information compiled or reviewed by Ms Jillian Irvin of Entech Pty Ltd who is a Member of the Australian Institute of Geoscientists. Ms Irvin consents to the inclusion. Ms Irvin has sufficient experience relevant to the style of mineralisation, type of deposit under consideration and to the activity being undertaking to qualify as Competent Persons as defined in the 2012 – Refer Edition of the “Australasian Code for Reporting of Mineral Resources”.

Cautionary Statement

The information contained in this document (“Announcement”) has been prepared by DEVELOP Global Limited (“Company”). This Announcement is being used with summarised information. See DEVELOP’s other and periodic disclosure announcements lodged with the Australian Securities Exchange, which are available at www.asx.com.au or at www.develop.com.au for more information.

The information in this Announcement regarding previous operations at the Woodlawn Project, including information relating to historic production, recoveries, mineral resources and financial information (including historical expenditure) has been sourced using publicly available information and internal data. While the information contained in this Announcement has been prepared in good faith, neither the Company nor any of its shareholders, directors, officers, agents, employees or advisers give any representations or warranties (express or implied) as to the accuracy, reliability or completeness of the information in this Announcement, or of any other written or oral information made or to be made available to any interested party or its advisers (all such information being referred to as “Information”) and liability therefore is expressly disclaimed. Accordingly, to the full extent permitted by law, neither the Company nor any of its shareholders, directors, officers, agents, employees or advisers take any responsibility for, or will accept any liability whether direct or indirect, express or implied, contractual, tortious, statutory or otherwise, in respect of, the accuracy or completeness of the Information or for any of the opinions contained in this Announcement or for any errors, omissions or misstatements or for any loss, howsoever arising, from the use of this Announcement.

This Announcement may include certain statements that may be deemed “forward-looking statements”. All statements in this Announcement, other than statements of historical facts, that address future activities and events or developments that the Company expects, are forward-looking statements. Although the Company believes the expectations expressed in such forward-looking statements are based on reasonable assumptions, such statements are not guarantees of future performance and actual results or developments may differ materially from those in the forward-looking statements. The Company, its shareholders, directors, officers, agents, employees or advisers, do not represent, warrant or guarantee, expressly or impliedly, that the information in this Announcement is complete or accurate. To the maximum extent permitted by law, the Company disclaims any responsibility to inform any recipient of this Announcement of any matter that subsequently comes to its notice which may affect any of the information contained in this Announcement. Factors that could cause actual results to differ materially from those in forward-looking statements include market prices, continued availability of capital and financing, and general economic, market or business conditions. DEVELOP assumes no obligation to update such information.

Investors are cautioned that any forward-looking statements are not guarantees of future performance and that actual results or developments may differ materially from those projected in forward looking statements. Please undertake your own evaluation of the information in this Announcement and consult your professional advisers if you wish to buy or sell DEVELOP shares.

This Announcement has been prepared in compliance with the JORC Code 2012 Edition. The ‘forward-looking information’ is based on the Company’s expectations, estimates and projections as of the date on which the statements were made. The Company disclaims any intent or obligations to update or revise any forward looking statements whether as a result of new information, estimates or options, future events or results or otherwise, unless required to do so by law.

Material Summary

Woodlawn Underground Mineral Resource Estimate

Material information summary as required under ASX Listing Rule 5.8 and JORC Code (2012) reporting guidelines.

Mineral Resource Statement

The Mineral Resource Statement for the Woodlawn Zinc-Copper underground Mineral Resource Estimate (MRE) was prepared during September and October 2023 and is reported according to the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (the ‘JORC Code’) 2012 edition.

The MRE includes 232,584 m of drilling from 1,150 diamond drill holes (DD), including reverse circulation with diamond tails, and 39 reverse circulation (RC) drill holes, completed since 1969. Of the drill metres underpinning the Mineral Resource, 17% were completed by Heron Resources Limited, 7% were completed by Develop with the remaining historical drilling completed by previous owners between 1969 and 2013. The depth from surface to the

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current vertical limit of the Mineral Resources is approximately 950 m.

In the opinion of Entech, the Mineral Resource evaluation reported herein is a reasonable representation of the global underground zinc, copper, lead, gold and silver Mineral Resources within the deposit, based on sampling drill data available as at 6 September 2023.

The Measured, Indicated and Inferred Mineral Resources are reported excluding historical mining voids and exclusion zones0F[1] , comprise wholly of fresh rock material and use a Net Smelter Return 1F[2] (NSR) cut-off value. The NSR cut-off values chosen to constrain and report Mineral Resource blocks were A$140/t for historical remnant2F[3] lenses and A$100/t for all other lenses. Entech considered these cut-offs to reflect values required to obtain metal recovery from the respective areas using mechanised underground mining methods. The Mineral Resource Statement is presented in Table 3 .

Table 3 - Woodlawn underground Zinc-Copper Mineral Resource, at NSR cut-off of A$100/t, with A$140/t used for remnant lenses

Mineral Resource Category	Tonnes (kt)	NSR (A$/t)	Zinc (%)	Lead (%)	Copper (%)	Gold (ppm)	Silver (ppm)

Measured	1,311	397	5.3	1.6	2.3	0.9	48.5
Indicated	5,918	336	4.9	1.7	1.9	0.4	34.6
Inferred	3,045	478	8.7	3.4	1.6	0.5	71.0
Total	10,273	386	6.1	2.2	1.8	0.5	47.2

The NSR has been calculated using metal pricing, recoveries and other payability assumptions detailed in ‘Cut-off parameters’ in Section 3 of the attached JORC Code Table 1. It is Entech’s opinion that all metals used in the NSR calculation have reasonable potential to be extracted, recovered and sold. Tonnages are dry metric tonnes. Minor discrepancies may occur due to rounding.

A total of 232,584 m of drilling from 1,150 DD and 39 RC drill holes was available for the MRE. This includes 83 new diamond drillholes completed by Develop since the 2022 MRE. Mineralisation interpretations were informed by 835 DD holes intersecting the resource and two RC drill holes intersecting the resource, for a total of 14,802 m of drilling intersecting the resource.

A breakdown of Table 3 , by NSR cut-off, is presented in Table 4 and Table 5 .

Table 4 - Woodlawn underground Zinc-Copper remnant Mineral Resource at an NSR cut-off of A$140/t

Mineral Resource Category	Lens	Tonnes (kt)	NSR (A$/t)	Zinc (%)	Lead (%)	Copper (%)	Gold (ppm)	Silver (ppm)

Indicated	A	77	357	6.9	3.1	0.8	0.6	52.4
	B	759	414	7.7	2.4	1.7	0.1	28.4
	C	738	467	7.7	2.1	2.4	0.4	39.4
	E	16	212	5.3	0.8	0.3	0.1	10.5
	J	243	356	3.8	1.0	3.0	0.1	23.4
Inferred	A	55	491	9.7	4.1	1.0	0.6	81.3
	B	467	544	11.0	3.3	1.8	0.1	37.0
	C	1,814	542	9.8	4.0	1.6	0.6	94.9
	E	16	339	6.3	2.4	1.2	0.7	17.5
	J	49	387	5.0	1.5	2.8	0.1	26.4
Total		4,234	488	8.7	3.1	1.9	0.4	60.5

1 Allion Partners. Co-operation deed. Heron Resources Ltd, Veolia Environmental Services Pty Ltd. 23 March 2017.

2 Net smelter return inputs and application to Mineral Resources are provided under Cut-off Grade and also ‘Cut-off parameters’ in Section 3 of the attached JORC Code Table 1.

3 Historical remnant lenses are defined as where greater than 20% of lens tonnage has been stoped using historical mining methods.

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Tonnages are dry metric tonnes. Minor discrepancies may occur due to rounding.

Table 5 - Woodlawn underground Zinc-Copper Mineral Resource excluding remnant material at an NSR cut-off of A$100/t

Mineral Resource Category	Lens	Tonnes (kt)	NSR (A$/t)	Zinc (%)	Lead (%)	Copper (%)	Gold (ppm)	Silver (ppm)

Measured	G	104	406	4.4	1.9	2.1	1.4	100.7
	K	1,207	397	5.4	1.6	2.3	0.9	44.0
Indicated	B	749	215	1.8	0.6	2.1	0.1	13.3
	D	1,430	371	6.3	2.6	1.3	0.8	51.9
	G	431	239	3.4	1.6	0.7	0.8	66.1
	H	78	574	5.5	2.9	3.7	2.0	88.4
	I	549	273	3.9	1.2	1.5	0.7	27.6
	J	562	295	1.0	0.2	3.7	0.1	12.7
	K	202	156	2.8	1.1	0.7	0.1	6.7
	L	83	296	3.7	0.9	2.1	0.5	13.3
Inferred	B	364	250	4.1	1.8	1.0	0.4	30.9
	D	76	360	6.5	2.2	1.3	0.7	38.1
	H	135	162	2.9	1.9	0.5	0.0	19.6
	I	65	411	4.9	2.8	2.2	1.3	56.1
	J	0.4	127	0.1	0.0	1.7	0.1	6.4
	K	3	245	2.5	1.1	1.7	0.5	40.5
Total		6,039	315	4.2	1.6	1.8	0.6	37.8

Tonnages are dry metric tonnes. Minor discrepancies may occur due to rounding.

Note the B and J lenses comprise Mineral Resources which fall below the lowest elevation of historically mined drives. Entech considers, in these instances, material would be accessed by way of Develop capital development drives and not via re-entry into historical workings. Therefore, these lenses comprise both remnant (within historically mined elevations) and virgin Mineral Resources (below historical mining elevations).

Approximately 41% of the MRE tonnage falls within remnant areas (Table 4), whereby greater than 20% of lens tonnage has been depleted via historical mine workings.

This MRE comprises Inferred Mineral Resources which are unable to have economic considerations applied to them, nor is there certainty that further sampling will enable them to be converted to Measured or Indicated Mineral Resources.

Competent Person’s Statement

The information in the report to which this statement is attached that relates to the Estimation and Reporting of Mineral Resources at the Woodlawn zinc–copper deposit is based on information compiled by Ms Jill Irvin, BSc, a Competent Person who is a current Member of the Australian Institute of Geoscientists (MAIG 3035). Ms Irvin, Principal Geologist at Entech Pty Ltd, is an independent consultant to Develop Global Limited (Develop) with sufficient experience relevant to the style of mineralisation and deposit type under consideration and to the activities being undertaken to qualify as a Competent Person as defined in the 2012 Edition of the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves . Ms Irvin consents to the inclusion in the report of matters based on her information in the form and context in which it appears.

Entech undertook a site visit to the Woodlawn operations during September 2023. During the visit Entech inspected mineralised intersections from the Woodlawn deposit in drill core (Kate, B, D and the newly discovered N lenses) and in underground exposures (Kate lens at the 2490, 2460, 2440 and 2140 levels) and observed drilling, logging,

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sampling, QAQC and metadata collection operations. Drill core mineralised intercepts were reviewed in the core yard against received assay results for 23WNUD 047, 049, 058, 062 and B lens mineralisation within 23WNUD0011 was relogged by the Competent Person from 286.2 to 418 m downhole. Entech is of the opinion that observations made during the site visit reflect processes, procedures and mineralisation styles in place at the Project.

Drilling Techniques

Diamond (DD) drilling makes up 98% of Woodlawn underground resource drill holes, including surface parent, wedge holes and drilling from underground drill cuddies, providing intercept points to an average of 20 m × 20 m and maximum vertical depth of 720 m. Reverse circulation (RC) drilling makes up the remaining 2% of drill holes underpinning the MRE, all drilled from surface locations and to a maximum depth of 145 m. The RC drilling targeted up-dip extensions of lenses at 100 m × 50 m spacing and ad hoc exploration target testing.

All drill collar locations were initially pegged and surveyed using a hand-held GPS, accurate to ±3–5 m. The holes were normally accurately surveyed using an RTK-DGPS system later (±10 mm) by a licensed surveyor after the holes had been completed. Downhole surveys were taken every 30 m down the hole. All reported coordinates are referenced to the Woodlawn mine grid (WMG). The topography is relatively flat at the location of the drilling.

Exploration and resource drilling campaigns completed historically by Heron at the Woodlawn deposit from 2014 through to March 2020 comprised 21% (288 holes for 49,400 m) of total MRE drill holes. Entech noted a key focus for Heron was to infill and extend drill hole coverage of known lens mineralisation. Drilling prior to Heron (1969– 2013) comprises 64% of total MRE drill holes (818 holes for 149,318 m).

From November 2022 through to September 2023, Develop completed 74 diamond drill holes for a total of 33,504 m. Of the 74 holes, 16 were used for sterilisation and resource definition while the remainder focused on resource extension down plunge of known lenses as well as exploration targets to the north of modelled Kate, I, D and B lenses.

Sampling and Sub-Sampling Techniques

In the historic Woodlawn Mine, DD holes were sampled using a variety of core diameters ranging from BQ (36.4 mm) through to HQ (63.5 mm) whereas drilling by Heron Resources from 2014 to 2020 consisted of NQ/NQ2 (47.6 mm/50.6 mm) and HQ/HQ3 (63.5mm/61.1mm) with lesser PQ (85 mm). All recent coring activities by Develop have been completed with NQ2 (50.6mm). The DD core was oriented where possible and marked with 1 m downhole intervals for logging and sampling. The DD core recoveries during Develop’s drilling were generally fair to good, with an average recovery >98.5%. Sample bias due to loss of fine/coarse material is unlikely. Historical and recent holes were both sampled through a combination of 1 m downhole intervals or based on geological contacts around zones of mineralisation. The DD core was cut in half or quarter if metallurgical testing was required.

Historical RC drilling used a 4.5-inch (11.43 cm) bit and samples were collected on 1 m intervals. In waste zones, a spear sample was taken (composited to 4 m lengths) and in the mineralised zone, the 1 m sample was split using a riffle splitter. Most sample lengths are between 0.22 m and 1.0 m. Historical documentation states that RC recoveries were visually estimated, with most recorded as being close to 100%. Develop have not completed any RC drilling.

The sample security of historical drilling is not known, but most samples were assayed at the on-site laboratory and chain-of-custody is not a concern. Sampling by Heron from 2014 to 2020 and by Develop since 2022 was done by trained personnel following industry standard sampling procedures.

Sample Analysis Method

Prior to 2000, sample preparation and analyses by Jododex Australia Pty Ltd (Jododex), Australian Mining and Smelting Pty Ltd (AMS) and Denehurst Limited (Denehurst) were conducted on site at the Woodlawn laboratory (NATA accredited laboratory). No company QAQC samples were included in samples submitted to the onsite laboratory. From 2000 to 2013, sample analyses for RC and DD samples collected by TriAusMin Limited (TriAusMin) were conducted at ALS Orange, with some final analyses of pulps undertaken at ALS Brisbane. Sample preparation of RC chip and DD core samples involved drying, crushing and pulverising to 85% passing 75 µm. Heron introduced improved QAQC protocols from 2014 onwards with 1:20 sample pulps checked for grind quality by wet screening at 75 µm with a quartz flush after every sample.

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Multi-element analyses prior to 2000 were aqua regia hydrofluoric and perchloric acid digest with AAS or ICP determination of copper, lead, zinc, silver and gold with some re-analysis by XRD or XRF analysis for copper, lead, zinc, silver and gold. Gold was assayed by aqua regia with assays above 2ppm re-assayed by fire assay. No company QAQC samples were included in samples submitted to the onsite laboratory, but the laboratory inserted its own to manage quality of analyses.

From 2000 to 2013, TriAusMin, and Heron from 2014 to 2020, implemented similar analytical procedures for RC and DD core samples with analyses, completed by independent laboratory facilities off site. Gold determination was by fire assay at ALS Oranges with pulps sent to ALS Brisbane for multi-element four-acid digest with ICP-AES finish analyses 3F[4] . TriAusMin included Blanks and certified reference materials (CRMs) at a rate of about 1:30 samples. From 2014 Heron included (blanks, reference standards and duplicates) at a rate of 5:35 samples during ICP work. The number of gold and base metal CRMs submitted represents about 10% of the total samples assayed since 2000. No duplicates were taken due to majority of samples being from DD core.

Based on documentation review at the time of the 2022 MRE, Entech is of the opinion the sample preparation techniques and analyses are appropriate for the style of deposit, commodity under consideration and reflect standard techniques available at the time.

In 2023, Develop implemented similar analytical procedures for DD core sampled, with analyses completed at ALS Brisbane for multi-element four-acid digest with ICP-AES finish. Develop included Blanks, CRMs and field duplicates at the overall insertion rate of about 1:17 samples; 5.4% of all available samples drilled during 2023. This includes 2.9% CRMs, 1% duplicates and 1.7% blanks.

Entech is of the opinion that the available QAQC data for the Develop 2023 drilling is reasonable, and no serious bias or errors have been identified. The assay methods reflect current industry practice, even though insertion rates of QAQC samples fall short of standard targets. This is because the 2023 drilling campaign was still on going at the time of this MRE update and not all QAQC sample data was complete at the time. Check assays, umpire laboratory analysis and laboratory QAQC samples were also not supplied for review at the time of this MRE update.

Geology and Geological Interpretation

The Woodlawn deposit is a stratiform syngenetic polymetallic volcanogenic massive sulphide (VMS) deposit that is hosted within the central part of the mid Silurian to early Devonian Goulburn Basin: a deep water, back-arc basin which developed within Ordovician to early Silurian sediments of the Lachlan Fold Belt that hosts numerous metalliferous deposits. Woodlawn lies on the eastern limb of the asymmetric north-northwest plunging Woodlawn Syncline. Mineralisation for base metal (zinc, lead, copper) and precious metal (silver, gold) is hosted in regionally metamorphosed (greenschist facies) fine- to coarse-grained felsic to intermediate volcanic rocks, volcanogenic sedimentary rocks and minor carbonaceous shale, known as the Woodlawn Volcanics. The Woodlawn deposit comprises three mineralised horizons (Lower, Middle and Upper) hosting 13 known massive sulphide lenses within a 400 m × 600 m wide and 950 m deep northwest plunging corridor which remains open at depth (Figure 1 and Figure 2).

Develop’s 2022-2023 drilling coverage occurs along the northwest plunging corridor of mineralisation and has intersected down plunge extensions of known lenses and new areas of mineralisation to the north. Develop’s drilling campaign is ongoing, however drilling used to inform this MRE Update as 6[th] of September, has meant that 17 existing domains were updated in addition to interpretation and modelling of 12 new domains.

The updated and new domains occur within the Lower, Middle and Upper horizons. New domains were assigned to Lower, Middle and Upper horizons based on spatial orientation and proximity to known lenses. Updated domains comprised massive sulphide and stringer mineralisation extensions laterally or down plunge within B,C, D, J, H and I lenses.

Exploration drilling by Develop targeting extensions to the north of existing corridor has resulted in the discovery and interpretation of two new massive sulphide lenses increasing the number of known massive sulphide lenses from 11 to 13. The two new lenses have been provisionally assigned to the Lower Horizon based on proximity to B lens however further work on mineralogy and geochemistry is required to confirm the assigned horizon.

4 Multi-element analyses comprised Ag, Al, As, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Sc, Sn, Sr, Th, Tl, U, V, W, Y, Zn and Zr

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Mineralisation domains were interpreted primarily on geological and mineralisation characterisation models defined by downhole geological contacts, and were based on lithology, sulphide characterisation (and distribution), grade tenor, structural model and review of historical void geometries. Using this approach, two key mineralisation styles were interpreted, massive sulphide and stringer mineralisation. It was noted these styles were also historically documented by Heron and recognised by Entech during the site visit and review of drill core photographs. The two mineralisation styles comprise the following assemblages:

Polymetallic mineralisation: fine- to medium-grained, massive (and banded) pyrite–sphalerite–galena–lesser chalcopyrite, with the gangue mineralogy including iron, talc, quartz, chlorite, phlogopite, muscovite and barite.
Copper mineralisation: includes pyrite–chalcopyrite, lesser pyrrhotite as well as chlorite, quartz and calcite as massive sulphide and stringer veins.

Lithology and structure are considered the predominant controls on base and precious metals, and gangue (iron) mineralisation at the Woodlawn deposit.

Zinc, lead and copper mineralisation is primarily associated with the polymetallic assemblage in the massive sulphide lenses. The mineralisation often comprises massive pyrite and has splays and thickened zones, which may be associated with faulting. Massive sulphide mineralisation may contain assays grading above 20% zinc, with copper and lead grades of several percent.
The copper-rich assemblages are spatially located coincident within the massive sulphide footwall, or as stringer veins proximal to the footwall or hanging wall of the massive sulphides. It was noted by Entech that the stringer mineralisation style occurred primarily in felsic and metasediment hosts.
Gold and silver mineralisation is associated both with massive sulphide and stringer mineralisation styles. The tenor of these metals was primarily related to their location within the horizon (Lower, Middle or Upper) and not by mineralisation style.

Several northwest-trending faults impact the strike and dip continuity of known lenses. Entech noted multiple instances of lenses structurally offset by these faults both in documentation and mapping of underground drives. Entech used historical (Heron) structural modelling to ensure interpreted mineralisation continuity accurately represented localised lens offsets. Extrapolated faults with sparse drill hole support from the historical structural model have been superseded by new drilling information for mineralisation extensions at depth. In areas where mineralisation remained open at depth, down plunge continuity was extended to a maximum of 40m from the last drillhole intersection and lateral continuity (up or down dip) was extended <5m from the nearest drillhole. Lateral continuity assumptions have been made based on geometries and extents of known lenses.

Weathering surfaces remain unchanged from 2022 MRE with all drilling by Develop located along an exploration drive within the fresh horizon.

Weathering surfaces were created by interpreting existing drill logging for soil and oxidation state and were extended laterally beyond the limits of the Mineral Resource Model. Mineralised domains all lie below weathering surfaces in fresh material.

Entech relied on documentation (Heron), drill hole geological and assay meta data, drill core photograph review of historical (195 of 1,106 holes, of which 74% were drilled after 2014) and 74 drill holes logged and photographed by Develop personnel, 2022 MRE mineralisation wireframes and mining voids to evaluate geological, structural and mineralisation continuity.

Where new drilling identified massive or stringer mineralisation, domain interpretation of massive and stringer mineralisation was initially undertaken using all available drill holes in SEEQUENT Leapfrog Geo software. Intercepts correlating to massive sulphide and stringer mineralisation and underpinned by strike continuity implied from lithology wireframes were independently identified and manually selected in SEEQUENT Leapfrog Geo prior to creation of an implicit vein model. Interpretation was a collaborative process with Develop’s geologists to ensure Entech’s modelling approach aligned with project restart objectives, represented observations and understanding of geological and mineralisation controls.

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In all, 17 existing domains were updated and 12 new domains interpreted. New and updated massive and stringer mineralisation were grouped as per historical nomenclature into lenses B, C, D,K, H and I. The mineralised lenses are grouped by Lower, Middle and Upper Horizons as follows:

Lower: B,C and J lenses
Middle: D and Kate (K) lenses
Upper: H and I lenses

==> picture [467 x 257] intentionally omitted <==

Figure 1 Long section, looking north . Woodlawn zinc-copper deposit showing drill hole traces, sulphide domains and underground workings. Red domains and drillholes are incorporated in 2023 update

Note: Mineralised domains (as interpreted) do not represent Mineral Resource classification extents.

==> picture [461 x 253] intentionally omitted <==

Figure 2 Plan view . Drill hole traces, sulphide domains and underground workings. Red domains and drillholes are incorporated in 2023 update

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Note: Mineralised domains (as interpreted) do not represent Mineral Resource classification extents.

Entech noted the following metal correlation and zonation relationships, which were then volumetrically subdomained using probability based numerical modelling in Leapfrog.

Geospatial relationship between zinc, lead and copper in the massive sulphide. o Higher tenor zinc and lead grades were preferentially located on the northern flank of massive sulphide lenses, sub-domained for estimation purposes.
Higher tenor copper grades were preferentially located on the southern flank of massive sulphide lenses, sub-domained for estimation purposes. Copper tenor was evenly distributed within stringer mineralisation.
Gold and silver tenor was consistent within individual lenses. Variations occurred within horizon group. For example, the tenor of gold was significantly higher in the Upper horizon.

Estimation Methodology

Compositing approaches were selected to honour the mineralisation style, geometry, expected grade variability and potential mining selectivity. Drilling samples were composited to one metre lengths honouring lode domain boundaries. Composite (best fit) was used, whereby any small residual intervals less than one metre were divided evenly between the composites to mitigate metal loss.

Exploratory Data Analysis (EDA) of the declustered (15 mN, 5 mE, 15 mZ) composited zinc, lead, copper, gold and silver variables in the mineralised domain groups was undertaken using Supervisor™ software. Analysis for sample bias, domain homogeneity and top-capping was undertaken. Evidence for further sub-domaining of composite data by weathering or lithology boundaries, for the purposes of interpolation, was not supported by statistical and spatial analysis.

Assessment and application of top-capping was undertaken on the zinc, lead, copper, gold and silver variables within individual (and grouped) domains. Domains were capped to address instances where outliers were defined as both statistical and spatial outliers, presented below:

All domains - Zinc 15%. Lead 10%. Copper 15%.
Zinc, caps applied across Lower, Middle, Upper Horizons. < 1% metal reduction.
o Lead, caps applied across Lower, Middle, Upper Horizons. < 1% metal reduction.
Copper, caps applied in Lower Horizon. < 1% metal reduction
Individual Domains – Gold ranging from 4 to 15 g/t.
Caps applied in Lower. 2 % metal reduction.
o Caps applied in Middle. < 1% metal reduction.
Caps applied in Upper. 4 % metal reduction
Individual Domains – Silver ranging from 100 to 1000 g/t.
Caps applied in Lower. < 1% metal reduction.
o Caps applied in Middle. < 1% metal reduction. o Caps applied in Upper. 11 % metal reduction

Variography was undertaken on the capped, declustered zinc, lead, copper, gold and silver variables grouped by mineralisation style (massive, stringer) and horizon (Lower, Middle, Upper). Robust variogram models with a low to moderate nugget for zinc and lead (6–18%), copper (10%), gold and silver (6–22%) were delineated and used in Kriging Neighbourhood Analysis (KNA) to determine parent cell estimation size and optimise search neighbourhoods. Variogram and search parameters for zinc were applied to lead due to statistical and spatial similarities. It should be noted that although the maximum continuity modelled in the variograms ranged from 30150m, the bulk of spatial variability (~55%) and subsequent kriging weights was applied within 30–50 m in the Lower and Middle horizons and 10–30 m in the Upper horizon.

The maximum continuity ranges are:

Zinc and lead. Lower 150 m, Middle 60 m, Upper 20 m
Copper. Lower 60 m, Middle 130 m, Upper 30 m
Gold and silver. Lower 165 m, Middle 135-150 m, Upper 120 m.

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Interpolation was undertaken using Ordinary Kriging (OK) in GEOVIA Surpac™ within parent cell blocks. Dimensions for the interpolation were Y: 10 mN, X: 5 mE, Z: 10 mRL, with sub-celling of Y: 0.312 mN, X: 0.625 mE, Z: 0.625 mRL. The parent block size was selected to provide suitable volume fill given the available data spacing and mining selectivity. The drilling data spacing varies from nominal 15 m × 15 m spacing in the central area of the deposit and increases to exploration spacing of 80 m to test continuity of mineralisation at depth. Considerations relating to appropriate block size include drill hole data spacing, conceptual mining method, variogram continuity ranges and search neighbourhood optimisations (KNA).

A two-pass estimation strategy was used, whereby search ranges reflected variogram maximum modelled continuity and a minimum of 6, maximum of 12 composites for zinc, lead and copper, and a minimum of 6, maximum of 16 for gold and silver. The second search reduced the minimum composite required in the neighbourhood to 2 or 4 (informed by KNA outcomes), all other parameters (e.g. range and maximum composites) remained the same. All blocks which did not meet the criteria to trigger an estimate remained un-estimated and were excluded from classification.

Domain and sub-domain boundaries represented hard boundaries, whereby composite samples within that domain were used to estimate blocks within the domain. Global and local validation of the zinc, lead, copper, gold and silver variables estimated outcomes was undertaken with statistical analysis, swath plots and visual comparison (cross and long sections) against input data.

The 3D block model was coded with geological horizon, lens, mineralisation style, weathering, depletion, sterilisation and Mineral Resource classification prior to evaluation for Mineral Resource reporting. Regressions were calculated directly into the block model for density, sulphur and Net Smelter Return. Iron percent was estimated, via ordinary kriging, for mine planning purposes.

Classification Criteria

Mineral Resources were classified as Indicated and Inferred to appropriately represent confidence and risk with respect to data quality, drill hole spacing, geological and grade continuity and mineralisation volumes. In Entech’s opinion, the drilling, surveying and sampling undertaken, and the analytical methods and quality controls used, are appropriate for the style of deposit under consideration.

Mineral Resources were classified based on geological and grade continuity confidence drawn directly from:

Drill hole methodology, data quality, spacing and orientation
Geological domaining
Estimation quality parameters
Historical mining strike lengths, widths, stope orientations and remnant mining areas

Measured Mineral Resources were defined where a high level of geological confidence in geometry, continuity, and grade was demonstrated, and were identified as areas where:

Blocks were well supported by drill hole data, with drilling averaging a nominal 15 x 15m or less between drill holes,
Lenses for G and Kate (Measured) were intercepted on two sublevels and blocks are within 20-40m from a lens development drive,
Estimation quality, slope of regression above 0.8.

Indicated Mineral Resources were defined where a moderate level of geological confidence in geometry, continuity, and grade was demonstrated, and were identified as areas where:

Blocks were well supported by drill hole data, with drilling averaging a nominal 40 x 40m or less between drill holes,
Blocks were interpolated with a neighbourhood informed by a minimum of 8 samples.

Inferred Mineral Resources were defined where a lower level of geological confidence in geometry, continuity and grade was demonstrated, and were identified as areas where:

Drill spacing was averaging a nominal 60 m or less, or where drilling was within 80 m of the block estimate,
Blocks were interpolated with a neighbourhood informed by a minimum of 2 samples

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Consideration has been given to all factors material to Mineral Resource outcomes, including but not limited to:

Confidence in volume and grade delineation, continuity and preferential orientation mineralisation
Quality of data underpinning Mineral Resources,
Mineralisation continuity experienced during previous underground operations
Nominal drill hole spacing and estimation quality (conditional bias slope, number of samples, distance to informing samples).

The reported Mineral Resource was constrained at depth by the available drill hole spacing outlined for Inferred classification, nominally 950 m below surface topography. Mineralisation within the model which did not satisfy the criteria for Mineral Resources remained unclassified.

Mineral Resources that are not Ore Reserves do not have demonstrated economic viability. The MRE does not account for selectivity, mining loss and dilution. This MRE update includes Inferred Mineral Resources which are unable to have economic considerations applied to them, nor is there certainty that further sampling will enable them to be converted to Measured or Indicated Mineral Resources.

The delineation of Measured, Indicated and Inferred Mineral Resources appropriately reflect the Competent Person’s view on continuity and risk at the deposit.

Cut-off Grade

The Mineral Resource NSR cut-off grade for reporting of global zinc, lead, copper, gold and silver resources at Woodlawn was A$140/t for remnant areas and A$100/t for all other material. The MRE is reported exclusive of mineralisation which has been mined and mineralisation which was considered sterilised by adjacent historical mining.

The NSR of A$100/t is approximately 78% of the break-even stoping cut-off value underpinning the current (2023) Develop Life of Mine Plan (LOMP). The NSR of A$140/t for remnant areas reflects higher associated costs with metal recovery from remnant mining areas and was selected based upon discussions with Develop engineers and benchmarked against analogous peer operations (comparable deposit style, commodities, project maturity).

The NSR cut-off considers revenue from base (zinc, lead, copper percent) and precious metals (gold, silver ppm) and offsets site operating and sustaining capital costs, including underground operating development. Metallurgical recoveries are factored in the NSR calculation. The base metal and precious metals used in the NSR calculation all have reasonable potential of being saleable.

The NSR calculation adjusts individual grades for all metals included in the calculation by applying the following modifying factors, presented in Table 6:

Metal prices
Metallurgical recoveries
Payability factors, inclusive of concentrate treatment charges, metal refining charges, payment terms (concentrate), logistics costs and NSR royalties.

Table 6 - Key NSR assumptions

Metal	FX rate	Metal price	Recoveries	Payability factors

Zinc	A$0.72:US$1	US$3,956.12/t	92%	Concentrate treatment charges, metal refining, payment terms (concentrate), logistics costs and NSR royalties
Lead		US$2,224.28/t	85%
Copper		US$9,620.86/t	89%
Gold		US$1,877.76/oz	43%
Silver		US$22.83/oz	78%

The NSR has been calculated using metal pricing, recoveries and other payability assumptions detailed in Section 3 under ‘Cut-off parameters’ in the JORC Code Table 1. It is Entech’s opinion that all metals used in the NSR calculation have reasonable potential to be extracted, recovered and sold.

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Figure 3 Grade-tonnage curve for the Woodlawn underground deposit – Measured, Indicated and Inferred Mineral Resources

Bulk Density

This MRE contains dry bulk density data collected on drill core from 244 holes (between 2014 and 2023). Density measurements were collected on all samples sent to the laboratory, measured using water immersion density determination method for each sample. No density data were available for historical drilling. A total of 5052 density measurements were available for new drilling completed by Develop with approximately 12% falling within massive and stringer mineralisation.

The density samples were located between 19100 mN and 19800 mN, and 8800 mE and 9600 mE, and nominally from the surface to a depth of 950 m, providing a representative density profile between mineralised domains, and depth profile within a centralised portion of the Mineral Resource area (85% from Middle and Upper horizons). Analysis of the bulk density data indicated values between 1.68 and 5.2 g/cm[3] SG (specific gravity).

Entech derived a multi-element regression equation for bulk density which resulted in a +95% correlation between the original density value and predicted value. The formula uses coefficients for zinc, lead, copper and iron:

Regression formula = 2.5179 + Zn%0.0241 + Pb%0.0282 + Cu%-0.0014 + Fe%0.0460

The regression formula was applied in the block model on a block-by-block basis, using estimated zinc, lead, copper and iron values for the individual blocks.

Project History and Historical Mineral Resources

The Woodlawn zinc-copper deposit was discovered in 1969, with the open pit and underground mine developed by Denehurst from 1978 to 1998. During this period, approximately 13.8 Mt 4F[5] of ore was extracted from the open pit, underground and satellite deposits at average grades of 9.1% Zn, 3.6% Pb, 1.6% Cu, 0.5 g/t Au and 74 g/t Ag. The mine was closed in 1998, due to commodity prices, and Denehurst was placed into administration in 2003.

A tailings retreatment project commenced in 1992 with tailings processed from three contiguous tailings storage facilities (TSFs) known as North, South and West dams, with retreated tailings placed back in North dam.

5 Independent Technical Due Diligence Review Heron Resources Ltd – Woodland Project – New South Wales. Behre Dolbear Australia, December 2016.

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Following closure of the mine in 1998, Tri Origin Minerals acquired the project. Limited exploration occurred in the late 1990s and early 2000s, but from 2007 to 2013, completion of a 17-hole (DD) campaign led to the discovery of Kate and I lenses. In August 2014, TriAusMin merged with Heron Resources Limited and the underground mine and processing plant were restarted in 2018; and placed into care and maintenance in March 2020. In July 2021, Heron Resources Limited was placed into voluntary administration. Develop acquired the project from Heron Resources Limited in May 20225F[6] .

Lenses historically extracted (8–39% lens volume) include:

Denehurst: Lenses A, B, C, E
Tri Origin and Heron: Lenses D, G, H, I, J, K.

The last publicly reported MRE was the 2022 Woodlawn underground Mineral Resource6F[7] , prepared by Entech for Develop under the guidelines of the JORC Code, reported 7.3 Mt at 5.7% zinc, 1.8% copper, 2.0% lead, 0.6 g/t gold and 44.9 g/t silver.

By comparison, approaches to domaining, classification, RPEEE (sterilisation and NSR) undertaken by Entech for this MRE are similar to the approaches for Entech 2022, with new drilling, capital development and mine planning studies, which incorporate the use of an existing paste plant to fill historical voids, were considered for this update.

Assessment of Reasonable Prospects for Eventual Economic Extraction

Entech assessed the Woodlawn MRE, as reported, as meeting the criterion for reasonable prospects for eventual economic extraction based on the following considerations.

Mining

The Woodlawn MRE extends from the topographic surface to approximately 950 m below surface. This depth is supported by the areal extent of historical underground workings. Entech considers material at this depth, and at the grades estimated, would fall under the definition of reasonable prospects for eventual economic extraction in an underground mining framework.

It was noted that the Woodlawn inventory included 8.1 Mt7F[8] of material adjacent to, or within 10 m of, historical mining voids. The consideration of this material as either sterilised or as a Mineral Resource within the context of Reasonable Prospects for Eventual Economic Extraction (RPEEE) was considered material to MRE outcomes.

The process to define material as sterilised or Mineral Resource material included stamping into the block model all estimated blocks within 0 to 5 m and 5 to 10 m from open development and stoping voids, running MSO (Mineable Stope Optimiser) on all estimated material in remnant areas and holding discussions with Develop and Entech mining engineers on the likelihood of achieving access, on a lens-by-lens basis. A key assumption underpinning these discussions and caveats to accessing these Mineral Resources included Develop gaining re-entry to sections of historical workings (pre-2014). Entech included or excluded material based on the understanding that a re-entry plan, which includes paste filling of historical voids, is defined and planned for execution as part of the LOMP.

The Competent Person reviewed individual lenses against historical mining voids, MSO shapes and NSR cut-offs above A$140/t to identify contiguous areas on strike extents, up or down dip of historical mining which could be considered potentially extractable by Develop within a reasonable timeframe of 15 years. Using this approach approximately ~4.2 Mt of material from lenses A, B, C, E and J were incorporated as remnant Indicated or Inferred Mineral Resources. This comprises 41% of the tonnage in the Woodlawn Mineral Resources. All remaining material (~3.9 Mt) was classified as sterilised, not meeting RPEEE considerations, and is excluded from Mineral Resource tabulations.

Discussions with Develop included the use of paste fill to assist in reclamation of remnant material and this was taken into consideration during the assessment of RPEEE and classification approach. It should be noted that additional sterilised material may be re-incorporated into future Mineral Resources once paste filling processes are

6 ASX. DVP. 20 May 2022. Completion of Woodlawn purchase paves way for Develop to implement exploration strategy. 7 ASX. DVP. 2 August 2022. Woodlawn Updated Mineral Resource Estimate.

8 Entech tabulations. 8.17 Mt @ 9.6% Zn, 3.6% Pb, 1.7% Cu.

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implemented and access to remnant material, via historical workings, is achieved. The current delineation of Insitu Mineral Resources within the context of RPEEE appropriately reflects the Competent Person’s view on risk at the deposit.

The MRE is reported using two NSR cut-offs for remnant and virgin areas, being A$140/t and A$100/t, respectively. For the purposes of NSR determination, NSR values were calculated, using estimated zinc, lead, copper (percent), gold and silver values (ppm), on a block-by-block basis prior to implementing reporting cut-offs. The metal components of the NSR calculation all have reasonable potential of being saleable. Entech considers the two NSR cut-offs appropriately reflect costs associated with metal recovery from virgin and remnant mining areas and would fall within the definition of reasonable prospects for eventual economic extraction in an underground framework.

Entech understands Develop plans to implement similar scale mechanised underground mining methods as were used previously at Woodlawn. This assumption was based on discussions with Develop senior geologists and engineers. No mining dilution or cost factors was applied to the estimate. No factors or assumptions were made within the MRE with respect to the environment.

Variances to the tonnage, grade and metal of the Mineral Resources are expected with further definition drilling. The Mineral Resources may also be affected by subsequent assessment of mining, environmental, processing, permitting, taxation, socio-economic and other factors.

It is the Competent Person’s opinion that the proposed underground mining methods and cut-off grades applied satisfy the requirements for reasonable prospects for eventual economic extraction .

Metallurgy

Estimated metallurgical recoveries are based on historical recoveries at Woodlawn during its operation from 1978 to 1998, which is further supported by metallurgical testwork undertaken during the 2015-16 Feasibility Study by SRK Consulting8F[9] and an operational metallurgical review by Mineralis Consultants in 20209F[10] .

Metallurgical testwork was based on crushing and grinding underground mineralisation from the Kate lens to produce float concentrates for copper, lead and zinc to assess recoveries of saleable concentrates for each metal type. Mineralis observed that zinc’s performance was the most consistent of the three metals (copper, lead and zinc), with the worst result being 50% zinc concentrate at 70% recovery.

Develop is currently completing additional metallurgical testwork on drill core samples from the current drilling programme. This work is ongoing, and results are expected to be finalised in early 2024.

Estimated metallurgical recoveries are factored into NSR calculations. Total recoveries calculated in the NSR, inclusive of all concentrate products are 92% Zn, 85% Pb, 89% Cu, 43% Au and 78% Ag.

Entech understands that iron and sulphur both require monitoring for mine planning and metallurgical amenability purposes. Both variables were included in the final Mineral Resource block model. Entech was not aware of other deleterious elements which would materially affect eventual economic extraction of Mineral Resources.

No factors or assumptions were made within the MRE with respect to deleterious elements or by-product. Entech was not aware of deleterious elements which would materially affect eventual economic extraction of Mineral Resources.

Given existing testwork data Entech does not consider metallurgical amenability poses a material risk to the eventual economic extraction of the Mineral Resources. No metallurgical recovery factors were applied to the Mineral Resources or Mineral Resource tabulations.

9 Technical Report (NI 43-101) Feasibility Study for the Woodlawn Project, New South Wales, Australia, SRK Consulting, 2016. 10 Review of Woodlawn Metallurgical Operation, Mineralis Consultants, April 2020.

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