Lithium-Boron at Rhyolite Ridge Ioneer: Estimates 45% More Mineral Resources than Expected

On March 5, Ioneer Ltd (ASX: INR, NASDAQ: IONR) has announced a significant 45% increase in the estimated mineral resources at its Rhyolite Ridge Lithium-Boron Project in Nevada. This boost is based on new data from twelve drill holes completed in 2024, all within the fully permitted project area approved by the U.S. government last October. The project is backed by a $996 million loan from the U.S. Department of Energy’s Loan Programs Office.

This increase is expected to enhance the project’s economic prospects, especially since the new drill holes show some of the highest-grade lithium found so far in the B5 unit, also known as Stream 1. This section of the deposit is relatively shallow and flat, which could help reduce mining costs.

Bernard Rowe, Managing Director of Ioneer, emphasized the unique advantages of the project.

“Today’s updated Resource reinforces the remarkable flexibility of Rhyolite Ridge’s unique mineralogy. It allows Ioneer to match prevailing market conditions and blend our ore to produce a valuable boric acid co-product, whose market is separate from the Project’s primary lithium product,” Rowe said.

The ability to adjust production between lithium and boron based on market prices is a key advantage for Ioneer. With lithium prices currently lower, the company can focus more on extracting boron, which could make up 30-40% of the project’s revenue, while lithium is expected to contribute 60-70%.

Key Resource Estimates
The updated mineral resource estimates for the South Basin are as follows: See Table 1. Summary of February 2025 Mineral Resource Estimate – Rhyolite Ridge South Basin

• Total Resource: 510 million tons (Mt)
• Lithium Carbonate Equivalent (LCE): 3.97 million tons (Mt)
• Boric Acid Equivalent (BAE): 14.66 million tons (Mt)
• Measured & Indicated Resource for Stream 1: 152 Mt
• Measured & Indicated Resource for Streams 1 & 2 combined: 366 Mt

The mineral resource is divided into three streams based on boron and clay content, which determine how the material can be processed:

1. Stream 1: High in boron, low in clay
   • Resource: 179 Mt
   • Lithium Carbonate: 1.54 Mt
   • Boric Acid: 12.00 Mt
2. Stream 2: Low in boron, low in clay
   • Resource: 274 Mt

• Lithium Carbonate: 1.78 Mt
• Boric Acid: 2.25 Mt

1. Stream 3: Low in boron, high in clay (requires different processing methods)
   • Resource: 58 Mt
   • Lithium Carbonate: 0.64 Mt
   • Boric Acid: 0.41 Mt

Stream 3 presents a different challenge due to its high clay content. Ioneer is collaborating with EcoPro Innovation Ltd to develop a way to process this material efficiently. EcoPro is a global leader in battery materials manufacturing and has a recycling system for used batteries.

Large parts of the South Basin (100% INR owned) and the nearby North Basin (100% INR owned) have not yet been drilled, and the overall Resource is expected to grow substantially with additional drilling. 

Looking Ahead
This updated resource will be used to develop the project’s mine plan and economics, which are expected to improve as more of the inferred resource is upgraded to measured and indicated categories. This could significantly increase the project's ore reserves.

Large sections of the South Basin and the nearby North Basin, both fully owned by Ioneer, remain unexplored. The company expects the overall resource to grow substantially with further drilling.

Efficient and Environmentally Responsible Processing
The presence of clay minerals in the deposit determines the processing method. Streams 1 and 2, which are low in clay, can be processed using vat or heap leaching methods that allow for dry stacking of waste material. This method eliminates the need for tailings dams, which can pose environmental risks. Stream 3, however, requires a different approach due to its high clay content.

Column leach tests conducted by Kappes, Cassiday & Associates in Reno, Nevada, have demonstrated the effectiveness of these processing methods for Streams 1 and 2.

What's Next?
The updated mineral resource estimate, effective as of 14 February 2025, was prepared by Independent Mining Consultants, Inc. It complies with the JORC Code (2012), an international standard for reporting mineral resources.

With the backing of the Department of Energy and a significant resource increase, Ioneer appears well-positioned to advance the Rhyolite Ridge project, tapping into both lithium for electric vehicle batteries and boron for a variety of industrial applications.

This announcement was authorized by Bernard Rowe, Managing Director of Ioneer.