So far this year, the company has recovered eight diamonds over 100ct, with this the second largest after the 472ct diamond discovered earlier in April.
Lucara also announced that it would sell the 327ct and 472ct diamonds, along with other qualifying diamonds recovered this year, at an exceptional stone tender in June.
Bidders will be able to view the stones in Gaborone from June 10 until the tender closes on June 19.