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 ...

The gem is a carbonado, one of the toughest forms of natural diamond. Black diamonds are usually about 2.6 to 3.2 billion years old - a time before dinosaurs existed. The Earth itself is around 4. ...

Sophie Stevens, a jewelry specialist at Sotheby's Dubai, told the AP she believed the diamond could be from space. "With the carbonado diamonds, we believe that they were formed through ...