BlueRock said the stone was 4.58ct larger than the mine's previous largest diamond, although was still being valued.
CEO Adam Waugh said the discovery was "hot on the heels" of the February 1 recovery of an exceptional 8.97ct diamond, which had been independently valued at over US$50,000.
BlueRock's two previous record value stones were a 7.76ct stone sold for $10,070 per carat and a 10.58ct diamond sold for $7,047/ct.