JOHANNESBURG (miningweekly.com) – Recent infill drilling programmes, improved estimation techniques and detailed geological studies at London-listed Gem Diamonds’ majority-owned Letšeng diamond mine, in Lesotho, have resulted in a “significant” increase in the project’s indicated resource base, in tonnage, by 132%.
The project, in which Gem Diamonds has a 70% stake, now boasted a total indicated resource of 187.1-million tonnes – an addition of over 100-million tonnes to the initial indicated resource category.
This category had been extended in depth from about 100 m beneath the current pit bottoms to a new depth classification of around 350 m below the current mine pits on both the Satellite and Main pipe orebodies.
The recent programmes had also increased Letšeng’s indicated resource base, in carat terms, by 127%, to a total of 3.23-million carats, from a previous total of 1.42-million carats.
The company said in a market update on Wednesday that the extension had not only resulted in a significant increase in the indicated resource tonnage and contained carats but had also allowed for an increase in the Letšeng probable reserves, with the entire 22-year life-of-mine plan now classified as reserve.
Gross resources, inclusive of reserves, now totalled 25.54-million carats, with an average grade of 6.35 carats per hundred tonnes.
Letšeng’s probable reserves, meanwhile, had increased, in tonnage terms, by 67% to 131.9-million tonnes and, in carat terms, by 64% to 2.26-million carats.
“The average diamond price for the Letšeng probable reserves has also improved by 19% to $2 045/ct, from a previous average of $1 715/ct. [The higher] average reserve price reflects increased market pricing and improved recovery of large, high-value Type II stones,” said the diamond explorer.
The Letšeng mine is famous for the production of large, top colour, exceptional white diamonds, making it the highest dollar per carat kimberlite diamond mine in the world.
Since Gem Diamonds' acquisition of Letšeng in 2006, the mine has produced four of the 20 largest white gem quality diamonds ever recorded.