Rupert is South Africa's richest businessman.
Rupert and Oppenheimer remain the two wealthiest billionaires in South Africa.
Grindrod Limited is owned in part by Remgro Limited, Rupert's investment holding.
Despite the slump in his net worth, Oppenheimer still ranks as the second-richest man in South Africa.
The billion-dollar drop in his net worth brings his year-to-date wealth loss to $3.55 billion.
Grindrod is a freight logistics and shipping services company owned in part by Remgro.
Remgro has also completed the sale of a 30-percent stake in South Africa's largest wine and spirits producer, Distell Group.
Despite his year-to-date wealth loss, Rupert remains not only one of Africa's richest men, but also one of the world's richest billionaires.
The recent drop in his net worth brings his year-to-date wealth loss to $2.79 billion.
Richemont will examine the fair value write down pertaining to its investment in YNAP at $2.7 billion.
