Figure 10.25Excavation of a kimberlite pipe at the Jwaneng diamond mine in Botswana. Diamonds are found in the dark-colored kimberlite rock in the center of the pit, which outlines the neck of an ancient, eroded volcano. The diamonds and other fragments of the African continental keel found at Jwaneng were erupted from depths of more than 150 km, and the analysis of these fragments supports the chemical stabilization hypothesis illustrated in Figure 10.24. Jwaneng is the world’s richest diamond mine, producing 15.6 million carats (3120 kg) of diamonds worth over $2 billion in 2006. A major extension begun in 2010 is expected to yield 100 million carats worth approximately $15 billion over the life of the mine.