The presence of fluorescence can make buying diamonds a bit more challenging, especially when dealing with mounted stones. Medium to strong blue fluorescence can easily give the illusion of making an “M” color look like an “H” when mounted. The blue fluorescence has the ability to cancel large degrees of yellow to make a light yellow stone look near- colorless. When buying mounted diamonds, checking for fluorescence is an urgent requirement to adjust your estimate of value. Buying a mounted diamond is somewhat risky to begin with, but with medium to strong blue fluorescence, the true color could potentially be very disappointing. This is not to say that every medium to strong blue fluorescent diamond will be a lower color stone however. Fluorescence and color are separate characteristics and fluorescence can appear in any color of the grading system.