South Africa’s mining company Sibanye-Stillwater is forming a joint venture with Australia-based ioneer to develop the Rhyolite Ridge lithium-boron project in Nevada, Kallanish reports.

The deal expands Sibanye-Stillwater’s holdings in the United States where it has three existing operations, while also boosting its holdings in battery materials. It is the company’s second lithium project and its third in battery metals.

Sibanye-Stillwater will pay $490 million for a 50% interest in the developing project while ioneer will retain a 50% stake and operational control.

ioneer will provide Sibanye-Stillwater with an option to participate in 50% of the nearby North Basin for an additional $50m, if Sibanye-Stillwater opts in. That basin is contiguous with ioneer’s claims in the area but separate from Rhyolite Ridge in the South Basin. The North Basin was not included in the project given its different geological setting and early-stage exploration status.

The Australian company also agreed to a subscription agreement for a strategic placement of $70m of ioneer ordinary shares. The 145.9m placement shares were issued to Sibanye-Stillwater on 15 September. That part of the deal must be approved by ioneer shareholders in a 21 October 2021 vote.

Sibanye-Stillwater is “an excellent partner for ioneer to jointly realise the promise of Rhyolite Ridge,” James Calaway, executive chairman of ioneer, says in a statement. “With a strong strategic partner in place, we can now look to finalise the debt financing for the project and move towards construction.”

Neal Froneman, ceo of Sibanye-Stillwater adds that “Rhyolite Ridge is a world-class lithium project and we recognise its strategic value with the potential to become the largest lithium mine in the US.”

The Nevada lithium-boron mine is expected to produce about 20,600 tonnes/year of lithium carbonate or about 22,000 t/y of lithium hydroxide, along with about 174,400 t/y of boric acid over the mine’s 26 years of operation. Production is expected to begin in late 2023. The project will cover 3.8 square kilometres or 377 hectares.

ioneer wants to develop the mine and processing facilities in Esmeralda County, even as the US Fish and Wildlife Service says it intends to protect a rare Nevada wildflower under the federal Endangered Species Act. The company says its mine can co-exist with the Tiehm’s buckwheat and the company’s conservation and protection measures could aid the plant in its recovery.

The US Fish and Wildlife Service must offer a proposed rule before 30 September along with a public comment period. A final decision on the endangered species listing must be released by 30 September 2022. A proposed critical habitat rule must be proposed by 31 January 2022. The plant is reported only in about four hectares in the Silver Peak Range in western Nevada. It grows only in mineralised soils with high levels of lithium and boron.