According to the company, the Type IIa diamond has exceptional colour and clarity, and was recovered while processing fragmental kimberlite.
The diamond is likely to be sold along two other diamonds worth more than 100 carat.
Lucara also gave updates about its Karowe plant where the optimization project is being undertaken.
The company said that construction activities are near completion, and testing of the new XRT diamond recovery machines has been completed.
According to Lucara , the new recovery and XRT sections are to be integrated into the main treatment plant before April 2015.
Lucara Diamond CEO William Lamb said: "The recovery of this magnificent stone once again confirms the quality of diamonds contained within the Karowe resource. Timing of the sale of these exceptional stones is still to be decided."
