As a term, diamond with fluorescence means a diamond will glow (in blue) under a UV lamp when illuminated. The impact of blue fluorescence on price depends on its noticeability.

For some whiter color stones, fluorescence gives the stone a milky white appearance, which greatly lowers value. In some instances, the fluorescence is hardly noticeable and has minimal impact on the stone’s brilliance and value.

Fluorescence often adds value to yellow color stones as it gives the stones a whiter, brighter appearance. Some buyers regularly pay better prices for medium blue fluorescent “H” color and more yellow stones.

On the other hand, yellow fluorescence may require an additional 5 to 10% discount as it cause a diamond looks more yellowish.

See more on how to budget on Fluorescence.