The company said it was the 129th diamond larger than 100ct the Karowe operation recovered since mining started in. Of this tally, 12 diamonds were larger than 300ct, including the historic 1,109ct Lesedi la Rona and the 813ct Constellation, which sold for a record US$63.1 million.

"The recovery of this latest, high-value diamond attests to the remarkable nature of the Karowe orebody, which has consistently delivered large diamonds throughout its history, CEO Eira Thomas said.

The company expects to mainly mine the high-value south lobe in 2019, including contributions from the newly refined EMPKS unit, which is understood to be the source of the mine's two largest diamonds to date.

Karowe currently has openpit reserves of 2.6 million carats, with a mine plan extending out to 2026.

The company is completing a feasibility study that could expand mining underground and extend the mine's life to 2036 and beyond.

The company (TSX:LUC) is off to a positive start to 2019, gaining 9.52% to date, but is still down 41% compared to a year ago. The stock added 3.21% or C5c on Friday to close at $1.61, capitalising it at $638.38 million.