Orange diamonds take on their unusual color from exposure to nitrogen during the formation process. True orange diamonds are extremely rare, and most are variations of yellow or brown shades, such as the Golden Maharajah Diamond – a 65.57 carat stone with a color grade of Fancy Dark Orange Brown.

Color grading policy dictates that if a stone’s color is assessed to contain 25-50% orange, the diamond is considered “orange.” Less orange in its color will result in a grade of “orangy.”

The only truly famous orange diamond in existence is the Pumpkin Diamond. The 5.54-carat stone was discovered in South Africa, and might have come from an alluvial deposit. It was cut and polished by William Goldberg and sold at a Sotheby’s auction that same year. Ronald Winston – of the Harry Winston diamond company – paid $1.3 million for it. The stone’s color, as well as the fact that the sale took place a day before Halloween, inspired Winston to name it the Pumpkin Diamond.

Winston set his orange diamond in a ring, flanked by two smaller white diamonds. Actress Halle Berry wore it to the 2002 Academy Awards, where she won the Best Actress Oscar.

In 2010, Namakwa Diamonds’ alluvial operations in the North West Province of South Africa yielded a 7.53-carat diamond with a color grade of Vivid Orange. Heno Kruger, head of trading at Namakwa, said that the Vivid Orange diamond had sparked a level of participation in the tender at which it was sold that was “almost without precedent in recent years.”

The diamond was eventually knocked down for over $1.3 million, setting a record per-carat price of $176,713.