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Erdene Expands Mineralization at Zuun Mod Molybedenum-Copper Project

Drill Results

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www.erdene.com [email protected]

ERDENE EXPANDS MINERALIZATION AT ZUUN MOD

MOLYBEDENUM-COPPER PROJECT

Highlights:

• Drilling from surface to 150 metres depth returned multiple intersections of ore-

grade mineralization in areas modelled as waste

• High-grade intersections, greater than 0.1% MoEq1 were returned from multiple

holes over widths of 6 to 18 metres

• Hole ZMD-98 extended to 450 metres, intersected near continuous Mo and Cu

mineralization over 374 metres, averaging 0.066% MoEq

• Resource model will be updated with 2025 drilling results ahead of a planned

Preliminary Economic Assessment expected to be delivered in mid-2026

Press Release

Halifax, Nova Scotia

2026.02.17

Erdene Resource Development Corporation (TSX: ERD | OTCQX: ERDCF | MSE:

ERDN) (“Erdene” or the “Company”) is pleased to announce results from drilling and

to provide an update on technical and economic studies at its wholly owned Zuun Mod

(“ZM”) molybdenum-copper project, 35 kilometres east of the Bayan Khundii Gold Mine,

in the Khundii Minerals District in southwestern Mongolia (See Figures 1 and 2).

Quotes from the Company

Peter Akerley, Erdene’s President and CEO stated, “Recent drilling at Zuun Mod

confirmed continuity and improved the grade of molybdenum mineralization in near

surface zones of the deposit. Additionally, drilling at depth demonstrated continuity in the

northern portions of the deposit. These results should expand near surface resources at

Zuun Mod, and will be incorporated in a Preliminary Economic Assessment targeted to

be delivered in mid-2026.”

Mr. Akerley continued, “Improved infrastructure in the Khundii Minerals District and strong

molybdenum and copper demand support the development of the Zuun Mod deposit.

Simultaneously we are developing drill targets through deep geophysics for our Khuvyn

Khar copper discovery, which is part of the same large porphyry system.”

1 MoEq%=Mo% + Cu% * 0.27504 and assumes 83% Mo and 81% Cu metallurgical recoveries, and based on Mo price of US$15.4/lb

and Cu price of US$4.34/lb

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Zuun Mod Drill Program – Q4 2025

A 3,362-metre, 24-hole drill program was completed on the wholly owned Khuvyn Khar

license, which hosts the Khuvyn Khar copper porphyry system, including the Zuun Mod

molybdenum-copper deposit in late 2025. The program included 18 holes testing the

upper 150 metres of the Zuun Mod deposit, and one hole extension (ZMD-98), seeking

to improve confidence and continuity of molybdenum (“Mo”) mineralization in the North

Racetrack area, at depth. With the exception of the extension of hole ZMD-98, all holes

were drilled at an angle of between -45 and -60 degrees. Two additional holes (ZMD-162

and 163) were drilled to test copper (“Cu”) porphyry targets (see release here) and a

further three scout holes were drilled to test a gold prospect 3.8 kilometres west of the

Zuun Mod deposit. Results from this program will be incorporated into an updated mineral

resource estimate the will be used as the basis for a preliminary economic assessment

(“PEA”), scheduled to be delivered in mid-2026.

The near surface drilling intersected high-grade Mo and Cu mineralization within the

upper 130 metres vertically. Multiple holes returned grades exceeding 0.07%

Molybdenum Equivalent (“MoEq”) over downhole lengths of up to 112 metres, with

multiple holes ending in mineralization. The results support the updated resource model,

confirming both near vertical and sub-horizontal orientation of mineralization and infilling

areas previously modeled as having low or no mineralization.

Extension hole ZMD-98, located in a lower confidence northern portion of the deposit,

intersected nearly continuous molybdenum and copper mineralization, and ended in

mineralization at 450 metres depth. When combined with the previously reported results,

the hole returned 374 metres (76 to 450 metres) of 0.066% MoEq within the central

portion of the North Racetrack zone. Future drilling will focus on this high grade zone,

which remains open both vertically and laterally.

Taken together, these results are anticipated to positively impact the Project’s mineral

resources, building upon the update reported in October 2025 (see release here). A

summary of significant assay results are included in Table 1.

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Table 1 - Summary of Significant Assay Results - Zuun Mod Mo-Cu Deposit

Hole ID From (m) To (m) Width (m) Cu % Mo % MoEq % (3)

ZMD-98(1) 76 450(2) 374 0.058 0.050 0.066

Incl 324 338 14 0.096 0.121 0.147

Incl 408 426 18 0.094 0.113 0.139

ZMD-143T 40 74 34 0.048 0.043 0.056

ZMD-145T 76 126 50 0.061 0.050 0.067

ZMD-146T 71 84 13 0.038 0.059 0.070

ZMD-147 124 140(2) 16 0.131 0.100 0.136

ZMD-148 100 140(2) 40 0.050 0.055 0.068

ZMD-149 76 94 18 0.036 0.033 0.043

ZMD-150 94 122 28 0.028 0.072 0.079

ZMD-151 36 122 86 0.040 0.056 0.066

Incl 78 88 10 0.035 0.111 0.120

And 136 142 6 0.056 0.084 0.099

ZMD-152 112 130(2) 18 0.078 0.043 0.064

ZMD-153 38 130(2) 92 0.051 0.058 0.072

Incl 84 102 18 0.061 0.112 0.128

ZMD-154 72 110 38 0.074 0.058 0.078

Incl 80 88 8 0.111 0.136 0.166

ZMD-155 70 110 40 0.044 0.050 0.062

ZMD-156 8 120(2) 112 0.063 0.055 0.072

Incl 86 98 12 0.074 0.112 0.133

ZMD-157 84 125(2) 41 0.070 0.052 0.071

ZMD-159 20 40 20 0.051 0.046 0.060

ZMD-161 50 78 28 0.049 0.062 0.075

Incl 50 56 6 0.047 0.117 0.130

(1) ZMD-98 was extended from 150m to 450m.ZMD-98 0m to 150m results previously reported.

(2) Hole ended in mineralization

(3) MoEq%=Mo% + Cu% * 0.27504 and assumes 83% Mo and 81% Cu metallurgical recoveries, and

based on Mo price of US$15.4/lb and Cu price of US$4.34/lb

Zuun Mod – Preliminary Economic Assessment

Given prevailing market conditions and the longer-term outlook for molybdenum and

copper, the Company has begun work on a PEA for Zuun Mod. Today’s drill results will

be incorporated into an updated mineral resource model during Q1-2026, after which

mining studies will be undertaken, including optimization, preliminary design, fleet

selection, and scheduling. Metallurgical testwork is also planned for multiple zones of the

deposit to confirm recovery assumptions.

The development of infrastructure associated with the Company’s Bayan Khundii mine

and other operations in the surrounding district are expected to contribute positively to

the development potential of Zuun Mod, supporting transportation, supply chains, and

labor resources. Environmental and permitting studies will be undertaken in parallel

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throughout the year, alongside costing and financial modeling. The PEA is targeted for

completion in Q3 2026.

Khuvyn Khar Drilling Results

The northern portion of the Khuvyn Khar copper porphyry complex hosts a large area of

disseminated copper mineralization associated with an approximately 20 square

kilometre zone of hydrothermal altered intrusive units and breccias. Copper mineralized

intervals include hydrothermally altered intrusive breccias with potassic altered and

mineralized fragments suggesting a deeper source of mineralization. The highest-grade

copper mineralization was reported in January, in hole ZMD-162, which was designed to

expand on the mineralization intersection in ZMD-121, completed in late 2010. ZMD-162

returning 65 metres of 0.63% copper and 2.9 g/t silver mineralization, including a higher-

grade zone of 30 metres averaging 1.25% Cu and 6.1 g/t Ag.

A second hole, ZMD-163, targeting a near surface alteration zone to the north of ZMD-

162, intersected wide zones of anomalous Cu mineralization, including 24 metres of 0.1%

Cu and ended in anomalous Cu mineralization.

Further drilling is required to further test the Cu-porphyry potential of the Khuvyn Khar

prospect area. A program of deep geophysics is being developed to aid in the

interpretation of the very large Khuvyn Khar porphyry system and aid in identifying

additional drill targets.

Table 2 - Summary of Significant Assay Results - Khuvyn Khar Cu Prospect

Hole ID From (m) To (m) Width Cu % Ag g/t

ZMD-162 286 351 65 0.630 2.900

Incl 298 328 30 1.250 6.100

ZMD-163 8 104 96 0.074 -

Incl 24 48 24 0.106 -

AND 122 200(1) 78 0.049 -

(1) End of Hole

Sundown Gold Prospect

The Sundown gold prospect (“Prospect”) is located 3.8 kilometres west of the Zuun Mod

Molybdenum-Copper deposit on the Khuvyn Khar mining license. The prospect consists

of a series of narrow east-west trending oxidized quartz veins mapped along a strike

length up to 100 metres. Surface sampling conducted by Erdene over the Prospect

returned gold grades up to 5.5 g/t gold.

In December 2025, three scout holes (ZMD-164, 165 and 166) were drilled to test

separate targets spaced approximately 100 metres apart.

Two of these holes (ZMD-164 and ZMD-165) intersected nearly continuous elevated gold

values over the entire hole length, beginning from surface, including a 28 metre thick

stockwork zone comprised of fine-grained sulphide and silica veinlets cutting a monzonite

porphyry with including 5 metres of 0.19 g/t gold in ZMD-164. ZMD-165 intersected 3

metres of 0.27g/t gold and 4 metres of 0.20 g/t gold within the same stockwork veined

monzonite porphyry unit interested in ZMD-164.

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About the Zuun Mod Molybdenum-Copper Project

The Zuun Mod Molybdenum-Copper Project is located in Bayankhongor Province,

Mongolia, 180 kilometres northwest of a major mining district and the border with China,

the world’s largest copper and molybdenum consumer and steel producer. The 100%

owned 6,041-hectare mining license, underpinning the Project, was issued in 2011 and

is valid for up to an additional 60 years. The Project is located approximately 35 kilometres

east of Erdene’s Bayan Khundii Gold Project.

Erdene undertook a multi-year exploration program outlining the Zuun Mod molybdenum-

copper deposit, within the large Khuvyn Khar copper porphyry complex and identified

multiple copper and molybdenum prospects, within the outer rim of the 16-kilometre

circumference porphyry complex. Given the Company’s focus on its gold projects in

recent years, only modest exploration and technical studies have been conducted over

the Khuvyn Khar license since 2011.

In October 2025, Erdene released an updated resource statement for the Zuun Mod Mo-

Cu deposit. The updated mineral resource includes Measured and Indicated resources

of 271.1 million tonnes (“Mt”) grading 0.056% Mo and 0.064% Cu (0.073% Moly

Equivalence (“MoEq”)) for 439.2 million pounds (“Mlbs”) MoEq. As well as an Inferred

resource of 269.1 Mt grading 0.051% Mo and 0.059% Cu (0.070% MoEq) for 416.3 Mlbs

MoEq. The cut-off grade for the resource is 0.035% Mo and constrained to a conceptual

pit based on US$22/lb Mo. The MoEq was calculated using the following formula: MoEq%

= Mo % + Cu % * 0.27504 and assumes 83% Mo and 81% Cu metallurgical recoveries.

Please refer to the Company’s October 10, 2025, press release for further details.

Qualified Person

Peter Dalton, P.Geo. (Nova Scotia), Senior Geologist for Erdene, is the Qualified Person

as that term is defined in National Instrument 43-101 and has reviewed and approved the

technical information contained in this news release. All samples have been assayed at

SGS Laboratory in Ulaanbaatar, Mongolia. In addition to internal checks by SGS

Laboratory, the Company incorporates a QA/QC sample protocol utilizing prepared

standards and blanks. All samples undergo combined multi -element ICP-OES

(Inductively coupled plasma optical emission spectroscopy).

Erdene’s drill core sampling protocol consisted of collection of samples in 1 to 2 metre

intervals over the entire length of the drill hole, excluding minor post-mineral lithologies

and dykes as required. Sample intervals were based on meterage, not geological controls,

or mineralization. All drill core was cut in half with a diamond saw, with half of the core

placed in sample bags and the remaining half securely retained in core boxes at Erdene’s

Bayan Khundii exploration camp. All samples were organized into batches of 30 including

a commercially prepared standard, blank and either a field duplicate, consisting of two

quarter-core intervals, or a laboratory duplicate. Sample batches were periodically

shipped directly to SGS in Ulaanbaatar.

Reported intervals are apparent thicknesses, i.e., downhole widths. The Zuun Mod drill

hole (reported in this release) was dipping at 70 degrees. Additional study is required to

confirm true widths. Reported grades for intervals are weighted averages based on

length of sampling intervals. No top cut has been applied.

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About Erdene

Erdene Resource Development Corp. is a Canada-based resource company producing

gold at the high-grade, low-cost Bayan Khundii Gold Mine in underexplored and highly

prospective Mongolia. The Company has interests in a portfolio of precious and base

metal projects near the Bayan Khundii Gold Mine in the Khundii Minerals District, which

provides a robust organic growth pipeline. Erdene Resource Development Corp. is listed

on the Toronto (“ERD”) and the Mongolian stock (“ERDN”) exchanges and OTCQ X

Market (“ERDCF”). Further information is available at www.erdene.com. Important

information may be disseminated exclusively via the website; investors should consult the

site to access this information.

Forward-Looking Statements

Certain information regarding Erdene contained herein may constitute forward-looking

statements within the meaning of applicable securities laws. Forward-looking statements

may include estimates, plans, expectations, opinions, forecasts, projections, guidance, or

other statements that are not statements of fact. Although Erdene believes that the

expectations reflected in such forward-looking statements are reasonable, it can give no

assurance that such expectations will prove to have been correct. Erdene cautions that

actual performance will be affected by several factors, most of which are beyond its

control, and that future events and results may vary substantially from what Erdene

currently foresees. Factors that could cause actual results to differ materially from those

in forward-looking statements include the ability to obtain required third party approvals,

market prices, exploitation, and exploration results, continued availability of capital and

financing and general economic, market or business cond itions. The forward-looking

statements are expressly qualified in their entirety by this cautionary statement. The

information contained herein is stated as of the current date and is subject to change after

that date. The Company does not assume the oblig ation to revise or update these

forward-looking statements, except as may be required under applicable securities laws.

NO REGULATORY AUTHORITY HAS APPROVED OR DISAPPROVED THE

CONTENTS OF THIS RELEASE

Erdene Contact Information

Peter C. Akerley, President and CEO, or

Robert Jenkins, CFO

Phone: (902) 423-6419

Email: [email protected]

Twitter: https://twitter.com/ErdeneRes

Facebook: https://www.facebook.com/ErdeneResource

LinkedIn: https://www.linkedin.com/company/erdene-resource-development-corp-/

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www.erdene.com [email protected]