In a statement, the AIM-listed group said the makeable yellow diamond was recovered together with a 22 carat makeable white stone, and an 11 carat fancy light-pink stone.
The company said the diamonds will go on sale at the next tender which is scheduled to take place during May 2019, adding that further details of the sale will be included in its fourth-quarter production update.
Firestone noted that this is the second stone of around 70 carat recovered from the operation this calendar year, following the 70 carat white, makeable which was sold in a March auction at a record overall price for a Liqhobong diamond.
Paul Bosma, Firestone’s chief executive officer, commented: "It was a good weekend for us, recovering the 72 carat diamond as well as the two smaller, high-quality stones from within the northern, lower grade part of the pit. These recoveries will certainly assist in supporting the average value of the next sale in May."
In late afternoon trading, Firestone shares were 4.9% higher at 2.15p.