The largest diamond ever found was a carbonado from Brazil; named Sergio, the stone weighed 3,167 carats. (One carat equals one-fifth of a gram.) The origins of carbonados have long baffled ...

Black diamonds, or Carbonado diamonds, go back 2.6 billion to 3.8 billion years and some experts believe they may have been formed in supernova explosions. The diamonds lack traces of minerals fo ...