Diamond Fluorescence and Cut: How They Change the Price
Most people shopping for a diamond know about colour and clarity. Two things that change the price get far less attention: fluorescence and cut.
I asked diamond dealers to explain both.
What Is Diamond Fluorescence?
Some diamonds glow under ultraviolet light. That’s fluorescence. Like colour and clarity, it’s a permanent part of the stone.
Out in bright sun, the UV can make the colour look different for a moment. It’s temporary, and it goes back when you step inside.
Does Fluorescence Affect a Diamond’s Price?
Yes. At the high end, buyers prefer a diamond with no fluorescence. A stone with heavy fluorescence can look a little cloudy, with less sparkle. The dealer we spoke with puts the difference at about 10 to 15% between no fluorescence and medium or strong.
Why the Cut Matters
Cut is the hidden factor. It’s what gives a diamond its fire and sparkle.
A round diamond has two parts: the crown on top and the pavilion underneath. The flat face on top is the table. How big the table is, and how deep the whole stone is, decide whether the cut grades excellent. The facets also need to line up perfectly, from the crown to the pavilion.
What Is a Triple Excellent (3EX) Diamond?
Triple excellent means the cut, the polish and the symmetry all grade excellent. It’s the best a diamond can get.
The 2,492 Carat Diamond, and the Standard I Buy To
In August 2024, Lucara Diamond Corp showed off a 2,492 carat diamond from its Karowe mine in Botswana. It’s the second-largest rough diamond ever found, after the 3,106 carat Cullinan. Lucara finds giant stones like this with X-ray technology that recovers them before they break.
When I buy white diamonds for clients, I look for D to F colour, VVS clarity or better, and a triple excellent cut. That’s what brings out the brilliance.
Find Your Diamond
Fluorescence, cut, colour and clarity all move the price. I’ll help you find a diamond worth owning, and show you why I turn the others down. See our custom engagement rings, or how I work as your jewellery buyer’s agent.
Already own a diamond? Read is your diamond or gemstone worth anything?
Subscribe on the Vivid Jewels YouTube channel for more gem stories.
Got gold or jewellery you no longer wear? I also buy gold in Canberra.
Frequently Asked Questions About Diamond Fluorescence and Cut
Does fluorescence lower a diamond’s price?
It can. High-end buyers prefer no fluorescence, and heavy fluorescence can make a stone look a little cloudy. One dealer puts the difference at about 10 to 15% between none and medium or strong.
Is diamond fluorescence permanent?
Yes. It’s a permanent part of the stone. The colour change you might see in bright sun is temporary.
What does triple excellent (3EX) mean?
The cut, the polish and the symmetry all grade excellent. It’s the best a diamond can get.
What is the second-largest diamond ever found?
The 2,492 carat diamond Lucara Diamond Corp recovered at its Karowe mine in Botswana, shown in August 2024. Only the 3,106 carat Cullinan is bigger.
Got gold sitting in a drawer? Here’s how selling it works in Canberra.
