Gem Diamonds has unearthed a 163.91-carat rough from its Letšeng mine in Lesotho, its second 100-carat-plus stone this year.

The miner discovered the “impressive” yellow diamond on June 22, it said Monday. The company found a 122-carat, “exceptional quality,” D-color, type IIa rough at Letšeng in March.

Letšeng had previously been known for producing a large supply of rough diamonds over 100 carats. However, the number of stones in that category has been dwindling. Last year, the company recovered four diamonds of that caliber, versus six in 2021 and 16 in 2020.

The dearth of special stones has hit the miner’s revenue. In the first quarter, sales fell 30% year on year to $36.7 million, and the average price declined 22% to $1,431 per carat.