Northern Star Resources on Monday said it rejected a A$27 billion acquisition proposal from South Africa's Gold Fields, sending its shares up more than 9% as it deemed the offer undervalued the company. Gold Fields proposed to acquire 100% of Northern Star shares in a scrip-and-cash deal, where each Northern Star share would receive 0.3125 Gold Fields shares and A$7.25 in cash. The proposal, received on September 14, initially valued Northern Star at A$38.7 billion (approximately US$27.15 billion), representing a 22% premium to its closing price on September 11. Northern Star's board unanimously concluded that the proposal "significantly undervalued" the company and was "highly opportunistic," and informed Gold Fields last Friday that it was not appropriate to engage in further discussions.