Fluorescence
A diamond's tendency to emit visible light (usually blue) when exposed to UV radiation.
Definition
Fluorescence is a diamond's ability to emit visible light (most commonly blue) when exposed to ultraviolet radiation. About 25–35% of diamonds exhibit some degree of fluorescence, graded from None to Very Strong by the GIA. In rare cases, strong fluorescence can cause a diamond to appear hazy or oily in daylight. However, faint to medium blue fluorescence can actually improve the appearance of diamonds in the J-M color range by counteracting yellow tint.
Why it matters in ring design
Fluorescent diamonds are often priced 5–15% lower than non-fluorescent equivalents, creating a value opportunity for informed buyers. Medium blue fluorescence in lower-color diamonds (I-K) can make the stone appear whiter, allowing jewelers to offer better value without sacrificing appearance.