Ioneer Ltd (ASX: INR, Nasdaq: IONR) (Ioneer) is pleased to announce a further material improvement in project economics for its 100%-owned Rhyolite Ridge Lithium-Boron Project (‘Rhyolite Ridge’ or the ‘Project’) in Nevada, USA. Ioneer achieved material increases in lithium and boron production by decreasing leach retention time from three (3) days to two (2) days, and now to one and a half (1.5) days, while using the same quantity of acid. Throughout 2025, Ioneer has focused on increasing lithium yield (the quantity of lithium carbonate produced per tonne of sulphuric acid consumed) and optimising reagent efficiency.
The increased lithium production means the Project will produce approximately 9,500tpa of lithium carbonate/hydroxide that is not committed under existing off-take agreements.
The Project has a stable overall operating cost structure to produce lithium carbonate and battery-grade lithium hydroxide due to the scale and reliability of its boric acid revenue. Boron has remained one of the most stable natural resource commodities over many decades. Pricing assumptions remain unchanged with a minimal increase in initial capital expenditure ($15 million).
Note: unless stated otherwise, all annual production and economic parameters are for Years 1-25.
The updated stage one operation with reduced leach times and higher plant throughput resulted in materially improved project economics. The updated findings position Ioneer, on a lithium carbonate equivalent (LCE) basis, in the lowest cost quartile for lithium production globally with an estimated all-in sustaining cash cost to produce battery-grade lithium hydroxide of US$4,628 per tonne net of expected boric acid revenue in the first 25 years.
“By cutting our leach processing time in half, Ioneer will now deliver more critical minerals faster to our partners as we collectively work to strengthen American critical mineral supply chains. The Rhyolite Ridge Lithium-Boron Project continues to exceed our high expectations with its unique mineralogy and project economics,” said Bernard Rowe, Managing Director, Ioneer. “The need for additional production and processing has never been greater, and Rhyolite Ridge continues to deliver.”
Ioneer developed its newest mine plan based on the higher processing rate leading to an updated Ore Reserve and Mineral Resource also being reported today. The overall Reserve and Resource numbers are largely unchanged from the previous August 2025 estimate, which yielded higher boron and lithium output.
In June 2025, Ioneer published an Association for the Advancement of Cost Engineering (AACE) Class 2 capital cost estimate (-10%, +15%) with approximately 70% of the Project’s engineering complete of US$1,667.9 million, including a 10% contingency. The changes announced today do not materially impact the capital cost estimate or the processing plant design, increasing the capital cost estimate by just US$15 million.
Next Steps
• Secure equity financing to sit alongside U.S. Government debt ($996 million)
• Final Investment Decision once equity and debt are in place
• Construction Phase Expected to take approximately 36 months (including procurement of long lead items)
• First Production – 36 months from FID
• Pathway to future growth
