Rare Colors (7.28)
Diamonds do occur in every color of the spectrum but some are extremely rare. Intense green, red and blue for example are almost unheard of, but are occasionally available for the wealthy buyers and collectors. Any valuable fancy color diamond should always be purchased from a knowledgeable, reliable source or with the presence of a GIA Origin of Color Report (or other reputable lab document) for the purpose of authentication. Otherwise assume the stone to have been artificially treated, which brings its value down dramatically.