Diamond Fluorescence Explained: Does It Affect Value?

Published: 2026-03-31 | Author: Benny Gabay

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What Is Diamond Fluorescence?

Fluorescence refers to a diamond's tendency to emit a soft glow when exposed to ultraviolet (UV) light. Approximately 25-35% of all diamonds exhibit some degree of fluorescence, with blue being the most common colour. Fluorescence is graded on a scale from None to Very Strong on GIA and IGI certificates.

Fluorescence Grades

• None (NON) - No fluorescence. The most neutral option.
• Faint (FAI) - Very slight glow under UV. Virtually invisible in normal light.
• Medium (MED) - Moderate glow under UV. Rarely visible in daylight.
• Strong (STG) - Visible glow under UV. May affect appearance in some D-H colour diamonds.
• Very Strong (VST) - Pronounced glow. Can cause a hazy or oily appearance in some diamonds.

Does Fluorescence Affect Appearance?

For most diamonds (colour G and below), fluorescence has no negative impact on appearance. In fact, in I-J colour diamonds, medium to strong blue fluorescence can make the stone appear slightly whiter and more brilliant in daylight, as it counteracts the slight yellow tint.

The exception: in colourless D-F diamonds with strong or very strong fluorescence, some stones can appear slightly hazy or milky in certain lighting. This is relatively rare, but it is why premium colourless diamonds with strong fluorescence are sometimes discounted.

Does Fluorescence Affect Price?

Yes, fluorescence directly impacts pricing:

• In colourless diamonds (D-F): Medium to Strong fluorescence typically reduces the price by 5-15%, as some buyers view it as a negative. However, the appearance difference is usually invisible in normal conditions.
• In near-colourless diamonds (G-J): Faint to Medium fluorescence has little pricing impact. Strong fluorescence may offer slight discounts.
• In I-J colour diamonds: Medium blue fluorescence can actually add value by improving the apparent colour.

Is Fluorescence Good or Bad?

Neither. Fluorescence is simply a characteristic - not a defect. For budget-conscious buyers, diamonds with medium fluorescence in G-H colour can offer excellent value: the stone appears bright and white, and the price is lower than an equivalent non-fluorescent stone.

For collectors and buyers prioritising maximum resale value, None fluorescence is generally preferred for colourless grades.

Our Recommendation

At Diagem, our Nivoda-powered diamond search filters allow you to select fluorescence preference. For everyday jewellery wear, we recommend not ruling out diamonds with Faint to Medium fluorescence - the visual difference is minimal, and the value gain can be significant.

Browse our natural diamonds or lab-grown diamonds, or explore our Diamond Buying Guide for more guidance.

Related Reading

• Diamond Colour Guide
• Clarity: VVS vs VS vs SI