Have you ever been in a club where all the white shirts and blouses are so white they’re almost blue? That’s ultraviolet light and some diamonds react to light in a similar way.
From a practical point of view this means fluorescence can be used to ‘confuse the eye’ by adding this ‘blueing’ phenomena to what you see. This can be useful as it can make an ‘h’ color stone look like a good ‘g’ which is a neat budgetary play.
Our recommendation on carat weight is to listen to your partner as to what their priorities are but there’s quite a bit of information you should both know before finalizing your decision.
To avoid a potential problem of ‘lifelessness’ in a stone (and prevent over-paying), be sure to take in our video, ‘size vs weight’.
Unfortunately, those two words, ‘size’ and ‘weight’, are often used interchangeably when describing diamonds. So, let us start with a question. If we offered you a thousand dollars to tell us in 10 seconds the millimetre diameter (the size) of the particular carat (weight) diamond you’re looking for, would you know the answer?
If not, no surprise; maybe five clients in our 44 years have known this measurement, but the difference can be financially and aesthetically costly to you.
If we hadn’t raised this size versus weight issue, you might have focused on only the 4Cs and the price. You would probably have picked your cut shape, carat weight, color and clarity. You might well have known to pick only stones with a GIA certificate. Then you might have finished by building a spreadsheet of various sources and prices for that stone.
Let us show you what could easily happen if you took that route…
This is how most rough diamond crystals look as they come out of the ground. it’s called an octahedron.
If you look from the side it looks like this and, usually, the cutter will cut one big and one small stone from the rough, using the end bits to cut tiny stones.
From the top the rough crystal looks a bit like a pyramid from an airplane. Obviously the round shape of the diamond cannot be bigger than the rough crystal itself so will be the same measurement as the square. Let’s assume you’re looking for about a 2 carat round brilliant (although the principle is exactly the same for all sizes).
Imagine this rough crystal is 7.9mm across, which is perfect for cutting a properly proportioned 1.85ct but too small to cut a properly proportioned 2 carat. So, believe it or not, this presents the cutter with a difficult choice; to cut for beauty or to cut for weight.
Should he cut a knockout 1.85ct with the back cut like line ‘a’ or cut a less brilliant 2ct by cutting it too deep, like line ‘b’. No prizes for the answer, he cuts what the consumer is asking for, weight, making a bit more money in so doing, and that’s why there are, magically, way more exactly 2ct stones out there than 1.85s.




So, what’s best for the cutter might well not be best for you. After all, whichever stone he chose to cut from this piece of rough will be the same size (7.9mm diameter) even though they can be different weights.
The bottom line? If you buy this kind of deep-cut stone, although you are getting the weight you asked for, you’re not getting the size, the deal or the brilliance you expected.
So, when your girl is wearing this stone and compares it with her friend’s properly proportioned stone of exactly the same weight, the one you paid so much money for will be noticeably smaller and less brilliant.
We cannot tell you how often this happens and young ladies come into our galleries asking if something’s ‘wrong’ with their stone. Imagine how it feels from both your and her perspective when she learns how unnecessary and silly the difference is. After all, you’ve spent a fortune, thinking you chose well and negotiated a good deal. You probably got a certificate but no one talked about size versus weight. Your girl was overjoyed until she noticed it was not what either of you were told (or assumed) it was (although the information on the certificate was correct). Both of you now have a shadow over what should be one of the most joyful events in your lives.
So, is size versus weight important to you? Wouldn’t you have been better off spending less and getting the 1.85ct, or more to get the right size 2ct? Hey, you be the judge.
To be certain you get exactly the right weight (size) stone, either online or in-store, we can help. If you’re buying online, we suggest going to our help section to speak with one of our diamond specialists who will get back to you, after searching the market, with a selection of stones they believe fit your requirements.

If you’d like to personally examine and compare several stones yourself, click on our 'free hotel offer'. Make an appointment, come to any of our galleries and we’ll help you compare tenths of millimetres in size difference and you be the one who decides how many of those tenths are worth paying for.
Finally, be sure to turn this experience into a romantic interlude, after all it is a very big day!