It is the second largest stone mined from Kareevlei and the third valued at over US$50,000. The other two were a 7.76ct stone sold for $10,070 per carat in 2017 and a 10.58ct stone sold for $7,047/ct in 2018.
CEO Adam Waugh said two other high-quality stones had been recovered at the same time, a 6.36ct diamond and a 3.64ct stone.
The discovery came just after operations at Kareevlei restarted January 30 after a six-day suspension imposed by the department of mineral resources due to an accident.
BlueRock's shares rose 6.15% Tuesday to 0.34p (US0.44c).