Diamonds are produced at the Letšeng, Mothae, Liqhobong, and Kao mines, which combined are estimated to produce 240,000 carats of diamonds in 2014, worth US$300 million. The Letšeng mine is estimated to produce diamonds with an average value of US$2172/carat, making it the world's richest mine on an average price per carat basis. The sector suffered a setback in 2008 as the result of the world recession, but rebounded in 2010 and 2011. Export of diamonds reached US$230 million in 2010–2011. In 1957, a South African adventurer, colonel Jack Scott, accompanied by a young man named Keith Whitelock, set out prospecting for diamonds. They found their diamond mine at 3,100 m elevation, on top of the Maluti Mountains in northeastern Lesotho, some 70 km from Mokhotlong at Letšeng. In 1967, a  diamond (Lesotho Brown) was discovered in the mountains by a Mosotho woman. In August 2006, a  white diamond, the Lesotho Promise, was discovered at the Letšeng-la-Terae mine. Another  diamond was discovered at the same location in 2008.