Before diamond certification and standardization, the most sought after diamond colour was “blue white”. This term described the near colourless “ice” appeal of a diamond that emitted a strong blue fluorescence. This popular colour demanded a premium price.

It was later observed that strong blue fluorescence was also a quality sometimes found in hazy stones. This distinction was then taken advantage of by merchants who wanted to market lower quality diamonds. The market became flooded with these junk stones presented as high-quality “blue white” diamonds. After that, diamonds with blue fluorescence gained a bad reputation.

Today, the subject of diamond fluorescence is still a hotly debated issue with many misconceptions. Equipping yourself with the right knowledge about diamond fluorescence will allow you to make informed decisions on your diamond purchase. Read on to find out how you can enjoy a fluorescent diamond without the consequences.

What is Diamond Fluorescence?

Diamond fluorescence is simply the effect ultraviolet (UV) light has on a diamond. When a diamond is exposed to this long wave of electromagnetic radiation, the strength of fluorescence will depend on the amount of the trace minerals, such as boron, present in the diamond. Special UV lamps are used in the lab to check for this, but as UV light can also be found in sunlight, diamonds can also fluoresce (glow) under broad daylight which can affect the colour of the diamond to some extent.

Diamond Fluorescence

Image Credit: GIA

Factors to Consider About Diamond Fluorescence

1. Colour

About one third of all diamonds fluoresce a specific colour. Blue is the most common colour, followed by yellow, green, red, orange, and pink. If the fluorescence is of the same hue as the colour of the diamond, it will make the colour appear more intense and thus more desirable. In some cases, fluorescence can lift the colour to the naked eye, enhancing the beauty of the diamond.

2. Strength

The second factor to consider is the strength of diamond fluorescence. Laboratory reports will usually note diamonds as having None, Faint, Medium, Strong, or Very strong fluorescence. For diamonds with barely discernible fluorescence, some labs will report them under the term “Negligible”. According to a study conducted by the GIA Gem Trade Laboratory, the strength of fluorescence does not directly correlate to the colour of a diamond. That is to say, it is also possible for two diamonds with completely different colour grades to exhibit exactly the same strength of fluorescence.

Impact of Fluorescence to the Quality of Diamond

Depending on the fluorescence, the effect on the appearance and price of a diamond can either be negative, positive, or neutral.

The negative aspect is that some very strong fluorescence can make a diamond appear hazy. Less than 1% of diamonds that have fluorescence will have an oily/chalky appearance to them which will look as if the diamonds are dirty no matter how many times you clean it. However, the same hazy appearance can also happen in diamonds that don’t have fluorescence, especially when combined with certain gemmological features such as graining (irregularity in the crystal growth of a diamond). So this consequence cannot be used to generalize all diamonds with very strong fluorescence.

Diamond fluorescence can be positive in the following aspects:

  • Most diamonds with blue fluorescence tend to be 10-15% cheaper. This is because of the unfounded negative reputation over the years. In usual lighting conditions however, you will not be able to tell any difference with the naked eye. This can be a good way to get a diamond at a great price.
  • Blue fluorescence can make warmer (K, L, M, or N) coloured diamonds appear whiter than they actually are. Even within white diamonds (H, I, or J), fluorescence can sometimes make them look very close to the quality of colourless diamonds (D, E, or F) when brought out into the sunlight.

Fluorescence in most cases is just neutral. Some medium or strong fluorescence will not have a huge impact on the appearance of the diamond whether viewed under direct or indirect sunlight. In the GIA Fluorescence Study, it was found that the average person could not make a distinction between a diamond with fluorescence and a diamond without.

Bottom Line

It all goes down to preference! Whether you might want to buy a diamond with blue fluorescence or not is a matter of taste. Just keep in mind that when considering a fluorescent diamond, it is wise to compare them side by side with a non-fluorescent diamond. That way you get to see the overall look first hand. What’s important is that you are happy with the diamond you purchase, so inspect it yourself and consult with a diamond specialist to make sure you are making the right decision.

Learn more about diamonds in our series on the 4 Cs of diamond quality.