US- and Australia-listed Ioneer has delivered a material uplift in the economics of its Rhyolite Ridge lithium/boron project in Nevada, following optimisation work that cut leach times and unlocked higher plant throughput.

The updated mine plan shows a 38% increase in the unlevered life-of-mine net present value to $1.89-billion, while the unlevered internal rate of return rises to 16.8%. Yearly lithium hydroxide production in years three to 25 increases by 20% to 25 500 t, with boric acid output gaining 9% to 126 700 t.

All-in sustaining cash costs for lithium carbonate equivalent are estimated at $5 626/t, positioning Rhyolite Ridge “in the lowest cost quartile for lithium production globally”, the company said.

The gains stem from reducing vat leach retention time from three days to two, enabling a 25% increase in ore throughput – from 2.4-million tonnes a year to 3-million tonnes a year – by using surplus sulphuric acid more efficiently. “The updated Stage 1 operation with reduced leach times and higher plant throughput results in materially improved project economics, further enhancing the attractiveness of Rhyolite Ridge,” Ioneer stated.

Importantly, the improvements have been achieved without any increase in the project’s capital cost, which remains at $1.67-billion, nor changes to the processing plant design.

The project is now expected to generate average revenue of $725-million a year in the first 25 years, of which about $555-million will come from lithium and $170-million from boric acid. Earnings before interest, taxes, depreciation and amortisation margins are forecast at nearly 69% over that period.

Ioneer highlighted that the increase in lithium output leaves about 7 500 t/y of lithium carbonate or hydroxide uncommitted under existing offtake agreements, creating scope for additional supply into US and global markets.

Rhyolite Ridge, located in southern Nevada, is the only known deposit globally amenable to vat and heap leaching, reflecting its unique lithium-boron mineralogy. The large resource base also supports future expansion potential.