The Letšeng Diamond Mine, found in the landlocked Southern African kingdom of Lesotho, is owned by Gem Diamonds, Ltd. and the government of Lesotho, and at an elevation of 3,100 m (10,000 ft) it is the world's highest diamond mine. Production It is characterised by extremely low grade ore (less than /hundred tons) and is known for producing huge diamonds, having the highest percentage of large diamonds (greater than ), giving it the highest dollar value per carat of any diamond mine. The world average is roughly US$81 per carat, while Letšeng averaged over US$1,894 per carat for the first six months of 2007. Unusual for Africa, and due to the elevation, temperatures at the mine drop to -20 °C, and snowfalls are common in winter. Geography Climate Letšeng has an alpine tundra climate (ET, according to the Köppen climate classification). This means that Letšeng has a chilly climate with fairly cool temperatures throughout the year, even for Lesotho, and snowfalls can happen as well. The average annual temperature is , the average annual high temperature is and the average annual low temperature is . The warmest month, January, has an average temperature of and an average high temperature of . The coldest month, June, has an average temperature of and an average low temperature of . June is the only month with an average temperature below freezing, although the average temperature of July is exactly . Letšeng has an average annual precipitation of . However, like most of Lesotho and South Africa, this is not evenly distributed throughout the year. Letšeng has a wet season with abundant rainfall from October to March and a dry season with less precipitation from May to August - the coldest time of year. In terms of precipitation April and October serve as transitions between the wet and dry seasons. January is the wettest month, receiving of precipitation on average, while July is the driest month, receiving only of precipitation on average. Significant diamond finds Lesotho Promise On 4 October 2006 the 603 carat (121 g) white diamond, the Lesotho Promise was unearthed, which until the January 2018 discovery noted below was the largest reported find this century; at the time it was found it was the 15th largest diamond ever found. The stone is of an exceptional colour, rated D, the top colour for diamonds. Lesotho Brown Previously the largest diamond found at