Winspear shareholders on Sunday endorsed the raised C$5 (A$5.82) bid and tendered 91% of all shares after management earlier firmly rejected the original $4.25 offer.
De Beers is financing the C$301 million acquisition from the cash resources it has built up on surging demand for diamonds in the United States and from sales of its massive stockpiles.
The takeover is part of the diamond giant’s strategy to increase its diamond production, especially outside Africa, and wash its hands of “blood” diamonds.
Also firmly in its sights is Australian diamond producer Ashton Mining, which owns 40% of the Argyle diamond mine in Western Australia’s Kimberley region.
De Beers has made a $522 million bid for the company, which Ashton’s management has called opportunistic and undervalued.