Sandfire Resources has placed its shares in a trading halt at $4.275 while its biggest shareholder, OZ Minerals, is cashing out.
OZ is offloading the stock to institutions in a bookbuild run by Macquarie Securities, hoping to achieve a price of at least $4.20.
OZ has held a big stake in Sandfire since 2010 when it paid $100 million, or $3.58 a share, for a 19 per cent stake in the DeGrussa copper-gold producer.
At the time it was seen as a precursor to an eventual takeover of Sandfire by OZ, which has spent years looking for another asset to complement its Prominent Hill operation. However, without a clear strategy and faced with reluctance by Sandfire and its other big shareholder, South Korea's POSCO (15.2 per cent), to engage, OZ's position has been static.
OZ's stake has long been viewed as an overhang, much to the frustration of Sandfire.
The broker consensus for fair value of Sandfire shares is just short of $6 a share, and there will be an expectation the company's stock will be re-rated once the dust settles on OZ's departure.
Sandfire shares were up four cents to $4.275 before entering a trading halt while OZ shares were up 10 cents, or 2.71 per cent, to $3.79 before trading in its shares was stopped.