After reading it several years ago, I finally managed to find back Edward Jay Epstein's fascinating story about De Beers, Oppenheimer, and the diamond trade over the last 150 years. His book "The Rise and Fall of Diamonds", is unfortunately out of print, though. "New" editions starts at $200 at Amazon, but maybe I'll pick up a used one.
Also worth reading is his article "Have You Ever Tried to Sell a Diamond?".