Name of the Project
Rhyolite Ridge lithium/boron project.

Location
Esmeralda County, Nevada, US, about 23 km north-east of Dyer.

Project Owner/s
emerging lithium/boron producer ioneer (100%).

Project Description
Rhyolite Ridge is a fully permitted, construction-ready greenfield project that will mine and process lithium and boron on site. It hosts the only known lithium/boron reserve in North America and the largest undeveloped lithium/boron ore reserve outside of Turkey.

The October 2025 ore reserve is estimated at 266-million tonnes containing 2.03-million tonnes of lithium carbonate equivalent and 7.76-million tonnes of boric acid equivalent. The reserve supports an estimated 77-year mine life, with potential for further expansion.

The project is designed to process 3.4-million tonnes of ore a year and produce lithium carbonate, battery-grade lithium hydroxide and boric acid. Average lithium carbonate equivalent production over the first 25 years is estimated at about 24 500 t/y. Lithium hydroxide production from Year 3 to Year 25 is expected to average about 27 800 t/y, while boric acid production over the first 25 years is expected to average about 135 500 t/y.

Ore will be processed using commercially proven technology, including ore sizing, vat acid leaching, impurity removal, evaporation and crystallisation. The project will not require evaporation ponds or a tailings dam, with spent ore residue to be dry-stacked.

Potential Job Creation
About 500 direct jobs are expected to be created during construction, while the project is expected to create and support 275 to 300 permanent on-site positions during operations.

Net Present Value/Internal Rate of Return
The updated definitive feasibility study estimates an after-tax, unlevered net present value (NPV), at an 8% real discount rate, of $2.24-billion and an unlevered internal rate of return (IRR) of 18%. The after-tax, levered NPV is estimated at $2.30-billion, with a levered IRR of 23.2%. The estimated payback period is seven years from the start of operations.

Capital Expenditure
Initial capital expenditure is estimated at $1.68-billion, including a 10% contingency.

Planned Start/End Date
ioneer is targeting a final investment decision in the second half of 2026, with first commercial production expected in 2029. The project has an estimated 77-year mine life.

Latest Developments
On June 23, 2026, ioneer announced that it had entered into strategic, nonbinding letters of intent with Korea Overseas Infrastructure & Urban Development Corporation, or KIND, and Hyundai Engineering to advance the development of Rhyolite Ridge.

The parties intend to formalise their cooperation through memorandums of understanding, expected in July 2026. Hyundai Engineering's letter pertains to potential participation in engineering, procurement and design.

The letters do not create legally enforceable obligations for KIND or Hyundai Engineering to invest in or otherwise support the project, and there is no certainty that binding agreements will be concluded.

Key Contracts, Suppliers and Consultants
Fluor (definitive feasibility study and engineering, procurement and construction management); Caterpillar and Veolia (major suppliers); and Kemetco Research, Kappes Cassiday and FLSmidth (processing testwork).

Contact Details for Project Information
ioneer, tel +61 2 9922 5800 or email ir@ioneer.com.