The latest find is a 138ct top white colour type 2a stone and brings the total tally to 12, the highest number of large stones recovered from Letšeng in a year.

The largest diamond found this year was a 910ct D colour type 2a diamond, the Lesotho Legend,which was the second largest recovered in the past century and sold for US$40 million in March.

Gem's total tally of over-100ct stones for 2017 was seven.

The company's shares were up 1.75% Wednesday to £1.16 (US$1.48).