Reserves & Resources

Mineral Resource Statement and Parameters

A summary of the March 2023 Mineral Resource estimate is provided in the table below. Note that Mineral Resources are reported inclusive of the Ore Reserve described in Appendix B.

March 2023 Mineral Resource Estimate for Rhyolite Ridge South Basin



  1. mt = million tonnes; Li = lithium; B = boron; ppm = parts per million; Li2CO3 = lithium carbonate; H3BO3 = boric acid; kt = thousand tonnes.
  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 stochiometric conversion factor of 5.322, and boron is converted to Equivalent Contained Tonnes of Boric Acid (H3BO3) using a stochiometric conversion factor of 5.718. Equivalent stochiometric 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. Jerry DeWolfe, who is a full-time employee of WSP Canada Inc. (WSP; formerly Golder) and a Professional Geologist (‘P.Geo’.) with the Association of Professional Engineers and Geoscientists of Alberta (‘APEGA’), a “Recognized Professional Organization” included in a list promulgated by the ASX from time to time. Mr. DeWolfe has sufficient experience that is relevant to the style of mineralisation and type of deposit under consideration and to the activity that he has undertaken to qualify as a Competent Person as defined in the JORC Code (2012).
  4. All Mineral Resource figures reported in the table above represent estimates at March 31, 2023. 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 5,000ppm boron cut-off grade for HiB-Li mineralisation and 1,090ppm lithium cut-off grade for LoB-Li mineralization below 5,000ppm boron. 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 5,000ppm boron cut-off grade for HiB-Li mineralisation and 1,090ppm lithium cut-off grade for LoB-Li mineralization; mining cost of US$2.67/tonne plus $0.0059/tonne-vertical metre of haulage; plant feed processing and grade control costs of US$45.45/tonne of plant feed; boron and lithium recovery of 83.5% and 81.8%, respectively; boric acid sales price of US$700/tonne; lithium carbonate sales price of US$10,000/tonne; and sales/transport costs of US$160/tonne of product.

In December 2022, the United States Fish and Wildlife Service (USFWS) listed Tiehm’s buckwheat as an endangered species under the Endangered Species Act (ESA) and has designated critical habitat by way of applying a 500m radius around several distinct plant populations that occur on the Project site. ioneer is committed to the protection and conservation of the Tiehm’s buckwheat. The Project’s Mine Plan of Operations submitted to the BLM in July 2022 and currently under NEPA review has no direct impact on Tiehm’s buckwheat and includes measures to minimise and mitigate for indirect impacts within the designated critical habitat areas identified.

The mineral resource pit shell used to constrain the March 31, 2023, mineral resource estimate was not adjusted to account for any impacts from avoidance of Tiehm’s buckwheat or minimisation of disturbance within the designated critical habitat. Estimates run inside the avoidance polygons identified 29.4 Mt at 1,650 ppm Li and 9,000 ppm B (both HiB-Li and LoB-Li streams combined), reflecting approximately 8% of the March 2023 global Mineral Resource estimate for the Project. The tonnes and grade within the avoidance polygons have not been removed from the Mineral Resources for the March 2023 estimate. Environmental and permitting assumptions and factors will be taken into consideration during future modifying factors studies for the Project. These permitting assumptions and factors may result in potential changes to the Mineral Resource footprint in the future.

  • This field is for validation purposes and should be left unchanged.