Synthetic Diamonds

Fluorescent Synthetic Diamonds – Why Do Diamonds Glow?

Did you know that diamonds glow in the dark? Well, some of them, anyway. As it turns out, some diamonds have something called fluorescence, which lets them glow – but only sometimes. Fluorescence may not be one of the 4 C’s (which I’ve discussed in an earlier post), but there’s a lot of controversy surrounding it. It can affect the look – and the price – of a diamond. Fluorescence is especially interesting when talking about synthetic diamonds. Fluorescent synthetic diamonds are not only common, but fluorescence can even be used to identify them!

What is fluorescence?

Fluorescence is a glowing effect that happens naturally with certain animals and minerals. It works by absorbing some other form of light and spitting it back out at a lower wavelength, meaning it has less energy. With diamonds, this is caused by the presence of boron or nitrogen, but really anything that reflects light at a lower wavelength can be fluorescent. Fluorescence gets interesting when you shine UV (ultraviolet) light at it, something the human eye can’t see. (One example of UV light is the effect you see with a blacklight, which emits long-wave ultraviolet light!) The light that the fluorescent object sends back is visible to us, and comes in a variety of bright colors! That’s how we get those cool pictures of glowing jellyfish and scorpions, and that’s how it works with diamonds, too. 

Photo by Kiara Sztankovics on Unsplash
Synthetic diamonds and fluorescence

Fluorescence in diamonds is an interesting topic, for multiple reasons. First, as I mentioned earlier, you can actually tell if a diamond is synthetic based on its fluorescence. There are two things to look for when trying to determine if a diamond is synthetic or not based on fluorescence: color and pattern. When it comes to color, a normal, natural diamond will usually have blue fluorescence. Synthetic diamonds, on the other hand, can show other colors, like green, orange, or red. These fluorescence colors exist in natural diamonds, but are a lot less common.

Along with the color, another telltale sign of a synthetic diamond is the pattern of the fluorescence. When looking at the gem from the top, fluorescent synthetic diamonds will often show a uniform, cross-shaped pattern. Natural diamonds are formed deep within the earth, and experience pressure at different times from different angles, so fluorescent patterns will be uneven. In contrast, a synthetic diamond experiences uniform pressure and heat, making its fluorescence consistent and symmetrical.

Is it worth it?

Synthetic or not, though, there’s still the big question: is fluorescence good or bad? Well, the answer is… we’re not actually sure. Scientists disagree on this point, and opinions vary. Those who disapprove of fluorescence believe that non-fluorescent diamonds are “purer”, since there’s no possible way for the fluorescence to interfere with the look of the diamond. It’s been shown that strong fluorescence can make diamonds appear cloudy, as well, although this effect is rare even among strongly fluorescent gems. Fluorescence can also make a colorless diamond appear to have color (even in natural light), making it worth less.

Those who choose to side with fluorescence have some arguments of their own. For one, even if a diamond is strongly fluorescent, the fluorescence won’t make the diamond appear any different in most places. Most people can’t even tell the difference between a diamond with fluorescence and a diamond without it. Some even prefer for their ring to have a soft glow to it under ultraviolet light. But there’s more – just like how fluorescence can make a colorless diamond appear to have color, fluorescence can also make colored diamonds appear more colorless. Blue fluorescence, for instance, will cancel out the yellow in a diamond and make it appear less yellow to the naked eye! This can still be a bad thing, though, since it can make a diamond look like it’s worth more than it is.

“Diamonds fluorescing (Russia) 1” by James St. John is licensed under CC BY 2.0
Making the choice

As is normally the case with diamonds, fluorescence is just one of those things you need to find a personal taste for. Perhaps you want your diamond to light up like a Christmas tree every time you put it under a blacklight. Maybe you want it to be as colorless and pure as possible. Whatever you decide, always remember that a diamond is more than a sum of its parts. If you find the diamond that’s perfect for you, don’t worry about the smaller details – just get it!


Want to find out more about synthetic diamonds? Looking for advice in buying an engagement ring? Check out our previous posts to see what we’ve already talked about and follow us on social media to stay updated!