Under the deal announced on Tuesday, Sibanye offered 19.5 US cents, or 2.66 rand, per Aquarius share, a 56 percent and 60.3 percent premium to Monday closing prices in Johannesburg and London respectively. The offer values Aquarius at $294 million.
By 0808 GMT, Aquarius' shares in Johannesburg soared 41.18 percent to 2.40 rand, slightly below the offer price. The stock was up more than 43 percent in London. Shares in Sibanye advanced 5.5 percent to 18.92 rand.
The offer has the backing of Aquarius' board but requires its shareholders approval.
"The Aquarius board has resolved unanimously to recommend that Aquarius shareholders vote in favour of the transaction," Aquarius said in a statement.
