June 2 (Reuters) - Australia-based critical minerals

miner Ioneer ( IONR ) said on Monday the ore reserves at its

Rhyolite Ridge Lithium-Boron Project in Nevada have increased

fourfold, with nearly half of the mineral resource being

converted into reserves.

The ore reserve has quadrupled to 246.6 million tonnes from

60 million tonnes in 2020, the company said.

It contains 1.92 million tonnes of lithium carbonate

equivalent and 7.68 million tonnes of boric acid equivalent,

making it the world's largest lithium-boron reserve, Ioneer ( IONR )

added.

"It allows Ioneer ( IONR ) to match prevailing market conditions and

blend or prioritise ore to produce a valuable boric acid

co-product, whose market is uncorrelated with the project's

primary lithium product," Managing Director Bernard Rowe said in

a statement.

Lithium prices have plummeted more than 80% from their peak

in November 2022 due to a supply surplus, forcing companies to

idle mines and put projects on hold.

Ioneer ( IONR ) plans to prioritize high-boron ore in the first 25

years of production, during a low lithium price environment, to

maximize revenue from boric acid sales.

The upgrade of ore reserves comes months after Sibanye

Stillwater said it will not go ahead with the plans to

invest in the lithium project, owing to the rare metal's

plummeting prices.

Sibanye had agreed to set up the lithium joint venture with

Ioneer ( IONR ) in 2021, as part of its diversification into battery

metals.

Ioneer ( IONR ) estimates the total capital expenditure to complete

the project to be $1.67 billion.