Australia’s richest woman Gina Rinehart has stepped up her buying spree in Liontown Resources Ltd. to accumulate a total stake of 19.9%, close to the 20% threshold that would normally trigger a mandatory takeover offer.

Rinehart’s privately-held Hancock Prospecting Pty paid no more than A$3 a share for its latest slice of the junior lithium miner, according to the company’s statement on Wednesday. It previously held a 18.36% stake.

“Hancock now looks forward to having a prominent influence on Liontown’s future, as its largest shareholder,” the company said in the statement, adding it had “achieved its strategic stake objective.”

Hancock’s stake may complicate Liontown’s A$6.6 billion ($4.2 billion) takeover by Albemarle Corp., the world’s largest lithium producer, which has been conducting due diligence on the Australian company. A stake of 20% or beyond would mean the Australian company would need to make an offer for all the shares in Liontown.

Rinehart, the mining entrepreneur who built her fortune in iron ore, is betting on lithium just as consumption of the steelmaking material consumption in China deteriorates. Meanwhile, the demand outlook for lithium — a key battery ingredient — remains robust, driven by the clean energy transition.

--With assistance from Sybilla Gross.