The resource is now 360 million tonnes for 3.4Mt of lithium carbonate equivalent and 14.1Mt boric acid equivalent, with the cut-off grades unchanged at 1090 parts per million lithium and 5000ppm boron.

 

The latest resource builds on the previous high-boron lithium mineralisation that was estimated for the definitive feasibility study in 2020 and adds in low-boron lithium mineralisation zones for the first time.

 

The resource is contained within the area being permitted for development but remains open in three directions with more than half the South Basin undrilled, and there being no drilling in the even larger North Basin.

 

Ioneer said there was potential to process the low-boron mineralisation in the planned processing plant, or as a standalone process stream via a second processing facility.

 

Ioneer managing director Bernard Rowe said it was clear Rhyolite Ridge was already a multi-generational asset with plenty of scope for growth beyond its existing development plant.

 

The company has binding offtake deals in place, debt and equity commitments of nearly US$1.2 billion for the project it will share with Sibanye-Stillwater. 

 

Permitting is in the final stages. 

 

Ioneer expects to produce 20,600tpa of lithium carbonate/hydroxide along with about 174,400tpa of boric acid from Rhyolite Ridge over an initial 26-year mine life, with production due to commence in the second half of 2025.

 

The company hopes to make a final investment decision on Rhyolite Ridge by mid-year.

 

Shares in Ioneer were last traded at A30c, valuing the company at $629 million.