Shares in Australian lithium developer ioneer (ASX: INR) jumped after securing support from two South Korean engineering and infrastructure groups for its Rhyolite Ridge project in Nevada, a key US source of battery materials targeting production by 2029.
The stock climbed as much as 29% intraday on Tuesday before closing up 7.1% at A$0.158, its highest level since January, giving the company a market capitalization of A$461.2 million ($320 million).
Ioneer said Korea Overseas Infrastructure & Urban Development and Hyundai Engineering plan to formalize their cooperation through memorandums of understanding in July 2026.
Ioneer said the agreements build on its relationship with South Korea, which includes a supply agreement signed with EcoPro Innovation in 2021.
The partnerships add international backing to one of North America’s most strategically significant lithium projects as Western governments and automakers seek secure supplies of battery minerals outside China.
10 years in the making
Ioneer has been working on Rhyolite Ridge since 2016 and brought in Sibanye-Stillwater (JSE: SSW)(NYSE: SBSW) as a partner in 2019. However, the South African miner walked away in February 2025 from a proposed $490 million investment for a 50% stake in the project.
Rhyolite Ridge hosts the continent’s only known lithium-boron reserve and is one of only two such deposits globally, according to ioneer. The company has invested more than $220 million in the project since 2016 and completed more than 70% of its advanced engineering work. It’s s targeting a final investment decision in the second half of 2026.
Once operational, the project is expected to produce 27,800 tonnes a year of lithium hydroxide and 135,500 tonnes a year of boric acid, with all processing conducted on site.
