Northern Star Resources rejected an unsolicited A$38.7 billion (US$27.1 billion) takeover proposal from South Africa’s Gold Fields, the Australian miner announced on Monday.

The offer proposed 0.3125 new Gold Fields shares plus A$7.25 in cash per Northern Star share. Received on September 14, it was worth A$27.00 per share at the time but had fallen to A$25.19 on Gold Fields’ Friday close. The implied premium was 14%, while typical Australian takeovers need about 30%, according to Reuters.

Chairman Michael Chaney said: “Gold Fields has sought to acquire one of the world’s premier gold portfolios at a price that falls well short of what the Board considers to be its fundamental value and at a highly opportunistic time.”

Northern Star shares rose 10.6% to A$24.46 in early Monday trading, the highest since August 28, but still below the implied offer price. Activist investor Elliott Investment Management, with a 5.6% stake, urged a strategic review in June that could lead to a sale, and Northern Star appointed new CEO Suresh Vadnagra in July to start on October 5. Gold Fields’ response to the rejection has not been reported.