Walk into a jewelry store and you may hear that fluorescence is something to avoid. Browse online forums and you'll find heated debates. The truth about diamond fluorescence is more nuanced than most realize—and understanding it can actually save you money while getting a more beautiful stone.
What Is Diamond Fluorescence?
Fluorescence is the visible light some diamonds emit when exposed to ultraviolet (UV) radiation, such as sunlight or blacklights. About 25-35% of diamonds exhibit some degree of fluorescence. The most common color emitted is blue, though yellow, green, and white fluorescence also occur rarely.
GIA grades fluorescence on a five-point scale: None, Faint, Medium, Strong, and Very Strong. This grading appears on the GIA certificate but is considered an identifying characteristic rather than a quality grade.
How Fluorescence Affects Appearance
In most cases, fluorescence has no visible effect on a diamond's appearance in normal lighting conditions. A GIA study of over 26,000 observations found that the average person could not distinguish fluorescent from non-fluorescent diamonds in standard lighting. However, there are situations where fluorescence can have either a positive or negative effect:
When Fluorescence Helps
- Lower color grades (I-M): Blue fluorescence can counteract yellowish body color, making the diamond appear whiter and brighter in daylight. A faint yellow diamond with Strong Blue fluorescence can look a full color grade better
- Outdoor settings: Diamonds with medium to strong blue fluorescence can appear particularly vibrant in natural sunlight
When Fluorescence May Hinder
- Very Strong fluorescence in high color grades (D-F): In rare cases, very strong fluorescence can make a colorless diamond appear slightly hazy or "oily" in direct sunlight. This affects roughly 2% of strongly fluorescent diamonds
- Under blacklights: At clubs or certain venues, a fluorescent diamond will glow noticeably—some love this, others don't
Fluorescence and Pricing
Here's where fluorescence can work in your favor. The market typically discounts fluorescent diamonds by 3-15% compared to non-fluorescent equivalents, depending on the degree. For diamonds in the G-J color range with Medium Blue fluorescence, this discount is often unwarranted—the diamond looks identical (or even slightly better) to the naked eye, but costs less.
This makes fluorescent diamonds one of the best value opportunities in the diamond market. An educated buyer can leverage this market bias to get a larger or higher-quality diamond within their budget.
Our Expert Recommendation
Don't automatically reject fluorescent diamonds. Instead, evaluate each stone individually. For near-colorless diamonds (G-J), Medium Blue fluorescence is often a value advantage. For colorless diamonds (D-F), stick with None to Faint. And always view the diamond in multiple lighting conditions before purchasing.
At Prestige Diamonds in Paramus, NJ, we encourage clients to see diamonds with different fluorescence levels side-by-side. Our private consultation room allows you to view stones under various lighting conditions so you can make an informed choice. Visit us at 327 E State Route 4, or call (201) 488-4280.