Diamonds are a stunning complement to any engagement ring or jewellery collection. The gems’ timeless appeal is at the heart of luxury around the globe. However, before you choose a diamond-encrusted piece, it’s essential to understand diamond fluorescence — a coloured aspect that could influence the stone’s future value and desirability.

To help guide your next high-end diamond purchase, we will outline the pros and cons of diamond fluorescence, highlighting its science, the GIA diamond fluorescence chart, and the potential long-term valuation of fluorescent diamonds.

Diamond fluorescence definition

Diamond fluorescence refers to the glow a diamond emits under ultraviolet (UV) light, typically showing a blue tint. About one in three diamonds display some degree of fluorescence. In the 5% of diamonds with non-blue fluorescence, yellow and green hues may also appear.

The science behind fluorescence in diamonds comes from the elements present within these precious gemstones. Faint traces of nitrogen in the diamond’s structure can cause a blue glow, while boron results in a yellow tint when exposed to UV light.

The Gemological Institute of America (GIA) offers a diamond fluorescence scale to educate buyers on how fluorescence influences value and aesthetic appeal. The grades include ‘very strong’ and ‘strong’ (often cloudy), ‘medium’ (milky), ‘faint’, and ‘none.’ Surprisingly, diamonds in the ‘none’ category can sometimes lower the value per carat.

How diamond fluorescence affects appearance

Examples of rough-cut diamonds glowing under UV light

Diamond fluorescence can cause these sparkling symbols of luxury to glow in the dark or under UV light. This effect occurs when electrons in the diamond absorb energy from sunlight or UV lamps. As the electrons’ energy returns to normal levels, the diamonds emit a form of visible light (or fluoresce).

If you observe diamond fluorescence in sunlight, you may notice a duller or more vibrant appearance than expected. Fluorescence can also detract from or enhance a diamond’s colour, especially when the stone has a lower colour grade. Therefore, learning what to look for when browsing diamond jewellers can help you avoid unexpected surprises after making an investment.

Colour, one of the four C’s of diamonds, joins carat, clarity, and cut as important buying considerations. A gem’s tint can impact which diamond to buy and even help you determine if the diamond is real.

The pros and cons of diamond fluorescence

There are numerous pros and cons of diamond fluorescence. However, whether you purchase such a gemstone is more down to personal preference than any other factor.

Pros

Diamonds exhibiting fluorescence are generally more affordable than those without.

The trait can also occasionally enhance a diamond’s appearance by making it appear whiter and more brilliant. Some people may prefer this look and be drawn to the unique characteristics diamond fluorescence brings.

Cons

The potential haze of diamond fluorescence can limit a stone’s appeal. Strong fluorescence may cause the gems to appear milky, going against the classic image of bright, dazzling diamonds.

The market can perceive diamonds of this nature less favourably. While fluorescence does not affect your ability to proudly show off your diamond delights, it can affect the resale value and may influence your buying decision.

Does diamond fluorescence affect value?

Although diamond fluorescence is not one of the 4C grading considerations, some appraisers may adjust a diamond’s valuation based on its degree of fluorescence.

For diamonds with a colour grade between D-F, fluorescence may cause a 60% decrease in value. While less alluring, these stones offer an enticing option for those shopping with a budget.

Thanks to their blue fluorescence, diamonds with a colour grade between I-M can be valued more highly. This glow gives the impression of a whiter and more exclusive diamond by harmonising its yellow tint.

Market trends fluctuate, but one thing is clear: demure diamonds remain a wonderfully wise and effortlessly stylish choice. Subtle gems are also great for everyday diamond outfits, adding a touch of luxury to your daily looks.

Do lab-grown diamonds have fluorescence?

Lab-grown diamonds are precisely crafted, meaning this increasingly requested stone rarely displays fluorescence. Many people choose lab-grown diamonds because they offer greater confidence in quality, with fewer visible flaws and a lower chance of fluorescence than traditional diamonds.

However, these gemstones can still obtain fluorescence during their creation due to two processes. If the diamonds are altered by irradiation, small gaps may develop within their lattice structure — this can allow blue or green hues to show as the gem absorbs in new ways. Similarly, when the stones are exposed to high temperatures (over 500°C), nitrogen can bond with these fissures, resulting in diamond fluorescence.

How to choose a diamond with fluorescence

Your feelings towards diamond fluorescence may depend on the purpose behind your purchase.

If you’re investing in a high-quality diamond for your portfolio, you’ll likely prefer a gem with low fluorescence — these tend to come with a premium price.

Gift buyers (or prospective fiancés) may decide that a diamond with slight fluorescence, which may be hazy or milky, strikes the right balance between beauty and budget.

When shopping in person, we recommend viewing loose diamonds or diamond jewellery under UV lighting and the store’s conditions. Consulting a jeweller or gemologist can also provide valuable guidance into how diamond fluorescence affects the stone in sunlight.

Diamond collections at Robert Gatward Jewellers

A custom diamond engagement ring from Robert Gatward Jewellers

Whether you’re shopping for a style-conscious fiancé or hunting for your next investment, there are arguments for and against diamonds with fluorescence. Your final decision should be a personal one, taking into consideration everything we’ve highlighted.

Once you are ready to buy, we invite you to explore the diamond collections at Robert Gatward Jewellers. From tantalizing diamond rings to exquisite diamond necklaces, our experts are on hand to answer any questions about fluorescence and help you choose a piece that’s perfect for you or your loved one. Contact us directly or book an appointment in one of our stores today.