A profoundly curious gem is up for auction. The pear-shaped jewel called "the Enigma," cut with 55 gleaming sides, is dark and cryptic. The fine art company Sotheby's calls the unusual diamond "one of ...

Black diamonds found in only a few places on Earth may have crashed down from space in a kilometre-sized rock, according to new research. The diamonds, also called carbonado, are only found in Brazil ...