by Rockdiamond » Sep 11, 2019 HI All! There's so much discussion about fluorescence. IMO it's one of the biggest "wildcards" about assessing a diamond. Yellow diamonds with blue fluorescence are heavily discounted due to the fact that a percentage of fl diamonds are hazy. Also, blue and yellow are kind of opposite in terms of color- so some fluorescent yellow diamonds' color is not as pure as an inert diamond. But sometimes there are no ill effects, and the discount is not justified. I recently shot a video showing how a yellow diamond turns blue under a UV lamp- IMO, the fluorescent diamond in the video is one that does not suffer ill effects of fluorescence. But it clearly changes color!