Diatreme Resources (ASX:DRX) upgraded the mineral resource estimate for its Northern Silica project Si2 deposit in Queensland to 301.5 million tonnes from 272.5 million tonnes, according to a Tuesday filing with the Australian bourse.

The update indicates an expansion of the resource base at the deposit, with mineralization extending further towards the southeast, the filing said.

The update will also form the geological basis for the pre-feasibility study, which is in its final drafting phase, per the filing.

Shares fell 3% in afternoon trade on Tuesday and earlier hit their lowest since November 2020.