On Wednesday, the president sacked Nhlanhla Nene in a move that sent
the rand to record lows and sparked a sell-off in bank shares.
His replacement for less than a week, Mr van Rooyen, is a little-known MP.
The latest move sent the rand up almost 5% on Sunday night.
Mr Gordhan was widely respected when he served as South Africa's finance minister from 2009 until 2014.
