Colorless diamonds can command high prices as gemstones  A type of less valuable diamonds can be treated to remove all color  Only sophisticated tests can distinguish such treated diamonds from naturally colorless ones  However, only 2 percent of diamonds mined are of the colored type that can be successfully treated, and many of those are of insufficient quality to make the treatment worthwhile
Surely, ttherefore, the vast majority of colorless diamonds sold by jewelers are naturally colorless
the difficulty that a customer of a jeweler would have in distinguishing a naturally colorless diamond from a treated one is not taken into account