ioneer (ASX:INR) said the ore reserve at its Rhyolite Ridge lithium-boron project in Nevada increased by 186.6 million tonnes to 247 million tonnes, and around 48% of the mineral resource was converted into reserve, according to a Monday Australian bourse filing.

It is now estimated at 246.6 million tonnes at 1,464 parts per million (ppm) grade of lithium and 5,444 ppm grade of boron, containing 1.9 million tonnes of lithium carbonate equivalent and 7.7 million tonnes of boric acid equivalent, the filing said. The company projected a 95-year mine plan for stage one operations.

The company estimated all-in sustaining cash cost to produce battery-grade lithium hydroxide of $5,745 per metric tonne of lithium carbonate equivalent. The co-product, boric acid, would account for an average of 25% of annual revenue in the first 25 years.

The firm's managing director, Bernard Rowe, said the update made the project the largest lithium-boron reserve in the world.

The firm's shares jumped nearly 6% in recent trading on Monday.