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Diamond fluorescence is a natural characteristic that causes some diamonds to emit a soft glow when exposed to ultraviolet (UV) light. While it often raises questions, fluorescence has little or no effect on the appearance of most diamonds. Understanding how fluorescence works can help you make an informed decision and, in some cases, even find better value when choosing your diamond.
Diamond fluorescence is the visible glow that some diamonds emit when exposed to ultraviolet (UV) light. The glow is most commonly blue. This glow can sometimes give the diamond a hazy appearance. This hazy effect may offset the advantages of a high Cut and Colour grade. Therefore, diamonds with no Fluorescence are typically preferred.
Fluorescence is a completely natural characteristic caused by trace minerals within the diamond's crystal structure. It does not affect the diamond's authenticity, durability or structural integrity. Under normal indoor lighting, most fluorescent diamonds appear no different from diamonds with no fluorescence.
Diamond fluorescence is graded according to its intensity rather than its colour. The Gemological Institute of America (GIA) classify fluorescence into five intensity levels, ranging from 'None' to 'Very Strong'.
- None: No visible fluorescence under UV light.
- Faint (Faint Blue): A very slight glow that is rarely noticeable.
- Medium (Medium Blue): A moderate level of fluorescence that is usually only visible under UV light.
- Strong (Medium Blue): A more pronounced glow which may slightly affect the appearance of some diamonds.
- Very Strong (Very Strong Blue): The highest level of fluorescence. A small number of diamonds may appear slightly hazy or milky in certain lighting conditions.
These grades offer insights into the level of fluorescence present in the diamond, with some people preferring diamonds with little to no fluorescence to maintain clarity and sparkle.
Diamond fluorescence is neither good nor bad. For the majority of diamonds, it has little to no effect on appearance under normal lighting and is simply another natural characteristic recorded on the diamond grading report.
In diamonds with slightly lower colour grades, blue fluorescence can make the stone appear whiter in daylight, offering excellent value without compromising its beauty. In rare cases, diamonds with Strong or Very Strong fluorescence may appear slightly hazy or milky, particularly in higher colour grades, although this is uncommon.
Rather than judging a diamond by its fluorescence grade alone, it's best to consider the overall balance of cut, colour, clarity and carat. Viewing diamonds online through high-quality imagery or in person is the best way to assess its appearance and choose the right stone with confidence.
For most diamond engagement rings, fluorescence should be considered a personal preference rather than a concern. Many diamonds with faint or medium fluorescence look completely identical to non-fluorescent diamonds, making them an excellent choice.
Rather than focusing solely on fluorescence, prioritise a diamond with an excellent cut and a balance of colour, clarity and carat weight. These characteristics have a much greater influence on brilliance and overall beauty. Our diamond specialists are here to explain every aspect of a diamond's grading so you can make an informed decision.
We've helped over 15,000 customers across the UK find their perfect engagement ring with honest advice and exceptional craftsmanship. Browse our natural and lab grown diamonds online, or book a viewing for personalised guidance from our diamond specialists.
