Mining giant BHP Group on Thursday said it had made an all-share takeover offer for rival Anglo American, valuing the company at £31.1 billion ($38.9 billion).

Anglo American shares leapt at the market open and were 13% higher at 8:35 a.m. in London.

The company confirmed it had received an “unsolicited, non-binding and highly conditional combination proposal,” which it said it was reviewing with advisers.

Australia-based BHP, the biggest listed miner according to Companies Market Cap, said that the deal would deliver 0.7097 BHP shares per Anglo American share to Anglo American’s ordinary shareholders.

A combination of the firms would form a juggernaut in copper mining and the world’s largest player in the space, according to a Reuters analysis.

BHP in 2022 merged its dual-floated business into a single legal entity with a primary listing in Australia.

Markets had closed before the announcement Thursday morning.

The proposal would entail separate demergers by Anglo American of its shareholdings in Anglo American Platinum Limited and Kumba Iron Ore Limited to Anglo American shareholders, it said.

“The combination would bring together the strengths of BHP and Anglo American in an optimal structure. Anglo American would bring its assets and long-term growth potential. BHP would bring its higher margin cash generative assets and growth projects along with its larger free cash flows and stronger balance sheet,” BHP Group said.

This is a breaking news story and will be updated shortly.