London-listed Gem Diamonds, which owns and operates the Letšeng mine, in Lesotho, says it will maintain its full-year guidance on carat recoveries and sales, despite lowering its guidance for tonnes treated to between 4.9-million and 5.1-million tonnes.

In a trading statement for the six months ended June 30, the company notes that increasing electricity interruptions resulted in lower volumes of ore processed, while higher-than-expected internal basalt dilution in certain domains of ore that was treated had impacted on throughput.

To mitigate the impact of internal basalt dilution, and improve plant stability and large diamond recoveries, an operational decision was taken during the second quarter to open crusher gaps and to slow throughput in the processing plant.

Gem says the initial results of these actions have been positive on plant stability and recoveries.

Ore tonnes treated during the first six months of this year decreased by 1% year-on-year to 2.47-million tonnes, while carats recovered decreased by 2% year-on-year to 50 601 ct.

Carats sold increased by 3% year-on-year to 52 163 ct, but sales revenue decreased by 19% year-on-year to $71.6-million as the price per carat decreased by 22% year-on-year to $1 373.

"The global rough diamond market has experienced a downturn in 2023. A decrease in the number of large, high-value diamonds recovered, combined with market pressure has negatively impacted on the average dollar per carat and revenue achieved during the period," Gem points out.

It notes that the highest price achieved during the interim period was $282 889/ct for a 6.63 ct pink diamond – the third highest dollar per carat achieved for a Letšeng rough diamond.

The highest price achieved during the interim period for a white diamond was $34 441/ct for a 58.07 ct Type IIa diamond.

Twelve diamonds sold for more than $1-million each, generating revenue of $21-million, while two diamonds greater than 100 ct were recovered during the six months under review. One of these has already been sold, while the other will be sold during the third quarter of this year.

The company will publish its results for the interim period on August 31.