Erdene Reports Resource Increase at Zuun Mod Molybdenum-Copper Deposit

• Measured and Indicated molybdenum resources increased 22% to 333 million pounds; Inferred resources increased 95% to 300 million pounds
• Measured and Indicated copper resources increased 16% to 384 million pounds; Inferred resources increased 75% to 350 million pounds
• Overall resource base expanded approximately 50% compared to 2011 estimate based on additional drilling and structural reinterpretation
• Q4 2025 drilling will test expansion opportunities using angled holes and evaluate the Khuvyn Khar copper prospect
• Project located 180 kilometres from China and 35 kilometres from Erdene's Bayan Khundii Gold Mine

Erdene Resource Development Corp. (TSX:ERD; MSE:ERDN; OTCQB:ERDCD) is a Canadian resource company currently producing gold at the Bayan Khundii Gold Mine in Mongolia. The company maintains a diverse portfolio of precious and base metal projects concentrated in the Khundii Minerals District, creating a pipeline for organic growth. With operations in what remains an underexplored yet highly prospective region, Erdene has established itself as a Mongolia-focused producer with exploration upside across multiple commodities. 

Updated Mineral Resource Estimate

The updated mineral resource estimate for Zuun Mod was prepared by SLR Consulting Australia in accordance with National Instrument 43-101 standards. The resource base increased approximately 50% compared to the 2011 estimate. Measured and Indicated molybdenum resources now total 333 million pounds, a 22% increase, whilst Inferred resources increased 95% to 300 million pounds. Copper resources reached 384 million pounds in Measured and Indicated categories (up 16%) and 350 million pounds in Inferred categories (up 75%).

The increases resulted from additional drilling and reinterpretation of structural controls on mineralisation. Core relogging programmes conducted in mid-2025 incorporated oriented core data from 2023 drilling, identifying both sub-vertical and sub-horizontal vein orientations. Historical drilling used predominantly vertical to sub-vertical orientations. The updated resource model reflects both vein orientation systems.

The estimate used a molybdenum cut-off grade of 0.035%, with parameters including a molybdenum price of US$15.40 per pound, open pit mining costs of US$2.18 per tonne, processing costs of US$6.85 per tonne, and assumed metallurgical recoveries of 83% for molybdenum and 81% for copper.

President and CEO Peter Akerley stated:

"We are very pleased to report the updated resource, confirming Zuun Mod as one of Asia's largest undeveloped molybdenum-copper projects."

Q4 2025 Drilling Programme

The Q4 2025 drilling programme will employ angled drill holes at approximately 60 degrees to better intersect sub-vertical vein structures. Historical drilling at Zuun Mod used vertical to sub-vertical orientations. The company believes sub-vertical veins are under-represented in the existing drilling data. The programme aims to confirm vein orientation data and frequency of veins in the near-vertical vein system.

The drilling will also test the Khuvyn Khar copper prospect, located 2.2 kilometres northwest of the Zuun Mod deposit. Previous drilling at Khuvyn Khar intersected 34 metres of 1.3% copper and 9.2 grams per tonne silver at approximately 300 metres depth. Geological mapping and geophysical surveys have defined a copper mineralised zone trending over 900 metres.

The Zuun Mod porphyry complex spans 5 kilometres in diameter with a 16-kilometre circumference. The licence area contains multiple copper, molybdenum, and gold prospects. In addition to drilling, planned work includes process testing, infrastructure and utilities evaluations, and marketing studies.

Akerley commented:

"As we define the deposit further, we are continuing to progress marketing and technical studies to advance the project."

Molybdenum Market and Project Location

Molybdenum is used as an alloying element in stainless and specialty steels, where it improves strength, heat resistance, and corrosion resistance. The metal is utilised in construction, renewable energy, aerospace, defence, and advanced electronics sectors. Near to medium term demand is supported by China's transition towards higher-quality steels. Supply growth faces constraints due to limited scalable deposits, ageing mines, capital requirements, environmental considerations, and long development timelines. Global production is concentrated in China, the United States, Chile, and Peru.

Zuun Mod is located 180 kilometres northwest of China, the world's largest copper and molybdenum consumer. The 100% owned 6,041-hectare mining licence was issued in 2011 and is valid for up to 70 years. The project is situated 35 kilometres east of Erdene's Bayan Khundii Gold Mine in a region where infrastructure development is occurring.

Akerley stated:

"Molybdenum is highly valued as a critical mineral with growing demand in the advanced electronics, aerospace and defense sectors and expanding processing capacity in the region. The outlook for molybdenum is bullish and production from Zuun Mod is expected to be readily absorbed in the market."

The company noted proximity to molybdenum consumers in China, South Korea, and Japan, as well as emerging markets in Vietnam and Thailand where processing capacity is expanding.

Next Steps

Erdene has outlined several initiatives for advancing Zuun Mod. The Q4 2025 drilling programme will test expansion opportunities at the main deposit and evaluate the Khuvyn Khar copper prospect. The company plans to conduct process testing to optimise metallurgical recoveries and evaluate concentrate specifications. Infrastructure and utilities evaluations will assess power supply, water availability, and transportation options. Marketing studies are planned to establish commercial relationships. The mining licence provides tenure security through 2081.

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