Resource and Reserve

1. ktonnes = thousand tonnes (metric); Li = lithium; B = boron; ppm = parts per million; Li₂CO₃ = lithium carbonate; H₃BO₃ = boric acid.

2. Totals may differ due to rounding. Mineral Resources reported on a dry in-situ basis. Lithium is converted to Equivalent Contained Tonnes of Lithium Carbonate (Li₂CO₃) using a stoichiometric conversion factor of 5.322, and boron is converted to Equivalent Contained Tonnes of Boric Acid (H₃BO₃) using a stoichiometric conversion factor of 5.718. Equivalent stoichiometric conversion factors are derived from the molecular weights of the individual elements which make up Lithium Carbonate (Li₂CO₃) and Boric Acid (H₃BO₃).

3. The statement of estimates of Mineral Resources has been compiled by Mr. Herbert E. Welhener, a Competent Person who is a Registered Member of the SME (Society for Mining, Metallurgy, and Exploration) and is a QP Member of MMSA (the Mining and Metallurgical Society of America). Mr. Welhener is a full-time employee of IMC Inc. and is independent of Ioneer and its affiliates. Mr. Welhener has sufficient experience that is relevant to the style of mineralisation and type of deposit under consideration and to the activity 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’ (JORC Code 2012).

4. All Mineral Resource figures reported in the table above represent estimates at October 2025. Mineral Resource estimates are not precise calculations, being dependent on the interpretation of limited information on the location, shape and continuity of the occurrence and on the available sampling results. The totals contained in the above table have been rounded to reflect the relative uncertainty of the estimate.

5. Mineral Resources are reported in accordance with the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (The Joint Ore Reserves Committee Code – JORC 2012 Edition).

6. The Mineral Resource estimate is the result of determining the mineralized material that has a reasonable prospect of economic extraction. In making this determination, constraints were applied to the geological model based upon a pit optimization analysis that defined a conceptual pit shell limit. The conceptual pit shell was based upon a net value per tonne calculation including a 5,000 ppm boron cut-off grade for high boron – high lithium (HiB-Li) mineralisation (Stream 1) and a $11.13/tonne net value cut-off grade for low boron (LoB-Li) mineralisation below 5,000 ppm boron broke into two material types, low clay and high clay material respectively (Stream 2 and Stream 3). The pit shell was constrained by a conceptual Mineral Resource optimized pit shell for the purpose of establishing reasonable prospects of eventual economic extraction based on potential mining, metallurgical and processing grade parameters identified by mining, metallurgical and processing studies performed to date on the Project. Key inputs in developing the Mineral Resource pit shell included a 5,000 ppm boron cut-off grade for HiB-Li mineralisation, $11.13/tonne net value cut-off grade for LoB-Li low clay mineralisation and LoB-Li high clay mineralisation; mining cost of US$1.69/tonne; G&A cost of US$11.13/process tonne; plant feed processing and grade control costs which range between US$17.49/tonne and US$80.11/tonne of plant feed (based on the acid consumption per stream and the mineral resource average grades); boron and lithium recovery (respectively) for Stream 1: M5 80.2% and 85.7%, B5 76.6% and 85.3%, S5 75.4% and 80.9%, L6 72.3% and 75.6%; Stream 2 and 3: M5 65.0% and 78.0%, B5 76.6% and 85.3%, S5 45.2% and 83.2%, L6 29.4% and 74.9%, respectively; boric acid sales price of US$1,172.78/tonne; lithium carbonate sales price of US$19,351.38/tonne.

7. The mineral resource is reported inclusive of the mineral reserves.

1. The statement of estimates of Ore Reserves has been compiled by Mr. Joseph S.C. McNaughton, a Competent Person who is a Registered Professional Engineer in State of Arizona. Mr McNaughton is a full-time employee of IMC Inc. and is independent of Ioneer and its affiliates. Mr. Joseph McNaughton is responsible for the estimate, has sufficient experience that is relevant to the style of mineralisation and type of deposit under consideration and to the activity being undertaken to qualify as a Competent Person as defined in the JORC Code (2012).

2. The ore reserve estimates the result of determining the measured and indicated resource that incorporates modifying factors demonstrating that it is economically minable, allowing for the conversion to proven and probable. In making this determination, constraints were applied to the geological model based upon a pit optimization analysis that defined a conceptual pit shell limit. The conceptual pit shell was based upon a net value per tonne calculation including a 5,000 ppm boron cut-off grade for high boron – high lithium (HiB-Li) mineralisation (Stream 1) and a $11.13/tonne net value cut-off grade for low boron (LoB-Li) mineralisation below 5,000 ppm boron broke into two material types, low clay and high clay material respectively (Stream 2 and Stream 3). The pit shell was constrained by a conceptual Mineral Resource optimized pit shell for the purpose of establishing reasonable prospects of eventual economic extraction based on potential mining, metallurgical and processing grade parameters identified by mining, metallurgical and processing studies performed to date on the Project. The conceptual pit shell was used as a guide to the engineered quarry designs used to constrain the Mineral Reserves.

3. Key inputs in developing the Mineral Resource pit shell included a 5,000 ppm boron cut-off grade for HiB-Li mineralisation, $11.13/tonne net value cut-off grade for LoB-Li low clay mineralisation and LoB-Li high clay mineralisation; mining cost of US$1.69/tonne; G&A cost of US$11.13/process tonne; plant feed processing and grade control costs which range between US$17.49/tonne and US$80.11/tonne of plant feed (based on the acid consumption per stream and the mineral resource average grades); boron and lithium recovery (respectively) for Stream 1: M5 80.2% and 85.7%, B5 76.6% and 85.3%, S5 75.4% and 80.9%, L6 72.3% and 75.6%; Stream 2 and 3: M5 65.0% and 78.0%, B5 76.6% and 85.3%, S5 45.2% and 83.2%, L6 29.4% and 74.9%, respectively; boric acid sales price of US$1,172.78/tonne; lithium carbonate sales price of US$19,351.38/tonne.

4. Ore reserves are based on a block model that is 7.62m x 7.62m in plan and 9.14m high. The model block size used for the ore reserve estimate is based on selected mining equipment and approach used within the mine plan. As a result, the dilution and ore loss are incorporated within the block model.

5. Ore reserves reported on a dry in-situ basis. The contained and recovered lithium carbonate and boric acid are reported in the table above in metric tonnes. Lithium is converted to equivalent contained tonnes of lithium carbonate using a stoichiometric conversion factor of 5.322, and boron is converted to equivalent contained tonnes of boric acid using a stoichiometric conversion factor of 5.718. Equivalent stoichiometric conversion factors are derived from the molecular weights of the individual elements which make up lithium carbonate and boric acid. The equivalent recovered tons of lithium carbonate and boric acid is the portion of the contained tonnage that can be recovered after processing.