Learn about Fluorescence 

Fluorescence in some degree is common in a great percentage of diamonds. Fluorescence is a form of lumination that is created when a diamond is exposed to low or high wave ultraviolet radiation. Faint or medium fluorescence will rarely affect a diamond's appearance. Usually fluorescence is unnoticed by the human eye in ordinary light. Fluorescence can cause a diamond to appear less clear or slightly hazy if the diamond exhibits very strong or extreme fluorescence. When selecting your diamond it is best to choose a diamond that has no fluorescence or faint to moderate fluorescence. 

Diamonds that possess strong fluorescence in color grades lower than the color grade of H will often face up approximately one color grade better than a non-fluorescent diamond. Strong fluorescence can actually improve the appearance of diamonds that possess traces of color. Diamonds that possess strong fluorescence in colorless to very near colorless grades D through G sometime exhibit a noticeable luminescence which can give the diamond a hazy appearance. A strong or extremely fluorescent diamond can usually be purchased for 10 to 30% less than a diamond that possesses fluorescence that is moderate or better. Listed below is a list of abbreviations for describing strength of fluorescence.

N, NO, NON, - No Fluorescence
F, FB, FT, FA, - Faint or Faint Blue Fluorescence
SL, SLB, SLT, - Slight Fluorescence
M, MO, ME, MD - Medium or Moderate Fluorescence
S, ST, STB, STG, - Strong Fluorescence
E, EX, EXB, EF, - Extreme Fluorescence

Abbreviations vary slightly due to variables in database input.