Pure fancy orange diamonds are very rare, as it is more common to find an orange diamond with secondary hues.  Similar to pure red diamonds,  The Gemelogiacal Institute of America (GIA) rarely grades a stone as pure orange. Typically these modifying colors are brown, yellow or pink (in which the orange is the secondary color). If the stone's color is less than 25 percent orange, it will be deemed "orangy" instead. Orangy diamonds, diamonds that the orange color is secondary, are not difficult to come by in the market, but orange diamonds are highly uncommon.

Most orange diamonds are found in one of two places: South Africa or the Argyle mine in Australia. Fancy orange diamonds owe their unique hue to the presence of nitrogen - which is the same element responsible for the color in yellow diamonds. According to the Natural Colored Diamond Association, nitrogen atoms must be grouped in a hyper-specific way within the carbon lattice while the diamond is forming. When they are situated in this particular arrangement, they absorb blue and some yellow light, thus producing an orange appearance.

 Pumpkin Diamond. 5.54 carats / Fancy Vivid Orange

The Natural Colored Diamond Association explained that the 5.54-carat Pumpkin was largely responsible for the sudden spike in interest in orange diamonds around the late '90s.

Ronald Winston bought the gem at a Sotheby's New York auction the day before Halloween in 1997 for $1.3 million. A while back, the stone was already estimated to be worth roughly $3 million but today it is probably at least twice that much.

Halle Berry wearing the Pumpkin Diamond at the 2002 Oscars

Despite the pumpkin's somewhat small size, it boasts a vivid orange grading from the GIA, which makes it highly covetable. Winston set The Pumpkin into a ring between two smaller colorless diamonds. This piece generated buzz on the red carpet at the 2002 Academy Awards when Halle Berry sported it on the red carpet - the same year she accepted the award for Best Actress. A year later, it was featured in the Smithsonian's "Splendor of Diamonds" exhibition.