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The Kingdom of Lesotho is a mountainous enclave surrounded by the Republic of South Africa. Lesotho is a parliamentary constitutional monarchy. The currency is the Maloti which is pegged in value to the South African Rand. Diamonds are Lesotho's only significant mineral resource with 33 kimberlite pipes and 140 kimberlite dykes identified, of which 24 are diamondiferous.
Aerial view of Satellite and Main Pipes at Letšeng le Terai Mine
Letšeng Diamonds Proprietary Limited is owned 70% by Gem Diamonds and 30% by the Government of the Kingdom of Lesotho. Operated by De Beers between 1977 and 1982, Letšeng reopened operations in 2004 and was acquired by Gem Diamonds in 2006. The average elevation at the mine is 3,100m above mean sea level, making it the highest diamond mine in the world. The mine consists of two adjacent primary near vertical kimberlite pipes the Satellite and Main, with confirmed vertical depths of 495m and 655m respectively. The average grade of these resources is 1.72 carats per hundred tons (cpht). With approximately 14% of all stones being larger than 10.8 carats (ct), the production profile is more akin to that of an alluvial than kimberlite mine. The average price per carat achieved at Letšeng in 2007 was US$1 997 per ct, relative to an industry average of US$81 per ct. As such Letšeng is a remarkable mine producing some of the world’s remarkable diamonds including large gem quality diamonds that sell for the highest per carat price of any kimberlite mine. Historically 81% of Letšeng's revenue is from large diamonds (+10.8 ct) and 90% of the diamonds recovered are gem quality with a significant proportion graded as D colour. Some of the world's largest diamonds have been produced at Letšeng. Of note is the 601ct Lesotho Brown in the mid 1960s (world’s 16th largest diamond ever recovered), the 603ct Lesotho Promise recovered in August 2006 (15th largest diamond) and the 493ct Letšeng Legacy recovered in September 2007 (18th largest recovered).
Letšeng Diamonds markets all its diamonds through a tender process in Antwerp. The Lesotho Promise sold by Gem Diamonds in Antwerp for US$12.4 million and likewise the Letšeng Legacy for US$10.4 million.
The mine’s current processing capacity is 2.6 million tonnes per annum (tpa), which will double to 5.28 million tpa by mid 2008 after commissioning of the second treatment plant is completed and commissioned. This will make Letšeng the 7th largest kimberlite mine in the world by throughput. The present life of mine is optimised at 33 years.
Plant 1 at night
Plant 2
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