Global diamond producer Gem Diamonds’ Letšeng diamond mine, in Lesotho, yielded a high-quality 202 ct Type IIa-D colour diamond, the seventh diamond over 100 ct to be recovered this year.

The mine, it is claimed, is the highest dollar-per-carat kimberlite diamond mine in the world.

Gem Diamonds owns 70% of Letšeng and 100% of the Ghaghoo mine, in Botswana. Ghaghoo has been placed under care and maintenance until market conditions allow for restarting of production.

The Letšeng mine is well known for producing large, top-colour white diamonds. Since Gem Diamonds acquired the mine in 2006, it has produced over 60 diamonds larger than 100 ct, predominantly high-value white diamonds. Among the diamonds recovered are the 603 ct Lesotho Promise diamond, the 550 ct Letšeng Star diamond, and the 439 ct Letšeng Legacy. In addition, the mine has produced the 357 ct Letšeng Dynasty and the 314 ct Letšeng Destiny diamond.

The mine also produces high-quality pink and blue diamonds, with a rare blue diamond achieving a sales price of $603 047/ct in 2013, with a pink diamond achieving $187 700/ct in 2016.

From July to September, the Letšeng mine recovered a total of 30 774 ct, an increase of 23% from 24 999 ct in the second quarter of the year. The diamonds achieved an average price of $2 397/ct for the July tender – the highest achieved US dollar price a carat for a tender since September 2015. Gem Diamonds received an average price of $1 858/ct for the period, up 4% from $1 779/ct in the first half of the year.

A total of 24 diamonds sold for more than $1.9-million each in the period, each generating revenue of $56.9-million from January to September. The mine also experienced zero lost-time injuries, and the Letšeng mine has been injury free for over 365 days, as of October.

Gem Diamonds reports that, as part of its strategic focus on reducing diamond breakage, it has been working in collaboration with experts from tertiary education institution the University of Johannesburg for the deployment of innovative technologies.

The technologies are designed to reduce breakages by identifying diamonds within kimberlite before starting the crushing process. Another new development involves liberating diamonds through electrical pulse technologies. The technologies will reduce processing costs by materially decreasing the volume of material run through the crushing process, thereby lowering the cost per tonne of material processed.

Gem Diamonds CEO Clifford Elphick said in a statement in October on the company’s successful turnover that efficiency and cost reduction methods have allowed the company to have another successful year of diamond mining at Letšeng.

“The groupwide efficiency and cost-reduction review is progressing well and has already identified yearly and one-off cost savings of $20-million, which is an increase of $5-million . . . In addition, a number of innovative diamond identification and liberation technology initiatives are being actively pursued, and I look forward to updating the market on further progress during [the fourth quarter of the financial year].”

Strong demand for Letšeng’s large, high-quality white rough diamonds has continued, Elphick affirms.

The mine treated a total of 1.3-million tonnes of ore during the second quarter, 61% of which was sourced from the main pipe, and 39% from the satellite pipe. The balance of the ore – 300 000 t – was treated through contracting company Alluvial Ventures’ plant, which was sourced from the main pipe and low-grade stockpiles.