Ok so this week we are looking a bit into the Big C called carat weight. Most people in the public know the word but do not always understand what it is and the limited part it plays in the bigger picture of diamond buying. Let's have a brief look into this.

So as with most gems size matters, that is the weight of it and this is measured in carats. Gemstones are measured in this metric as 1carat(ct) equals 0.2grams, therefore carat weight is a more sensitive scale as the world of gems work in small numbers. So one gram of diamond would be a huge 5ct in the gem world!

My discussions will be limited to the natural gems as synthetic man made Diamonds are a completely different topic that I will address in future blogs. As diamonds form in nature the bigger size or weight they take the rarer they are and subsequently the more the cost. Our industry work all factors in play with pricing a diamond but weight being one the the main scales upon which price is determined. Scale jump roughly as per below picture with every weight range jumping 10-20% on average per carat. This means it is not incremental i.e. only the bigger part over a certain range but the price jumps for the complete weight per carat.

The bottom line is if we say use 1ct as an example the price would be about 20% higher than compared with a 0.94ct size diamond of the exact same character. The difference in the diameter is well very little using the above example you would likely have a 0.1mm diameter difference between an 0.94ct vs a 1ct with a big price difference. Now in saying this if you put both stones next to each other unmounted our eyes will likely pick it up. Again this is when you compare right next to each other in a focused environment. Now the main thing here would be the mental side of knowing it is a 1ct diamond as this has been ingrained in us so the size or weight jumps make for landmarks say I want 1/2 carat or 3/4 carat or 1ct . These weight points have been carefully marketed and they tend to have big price jumps at these levels.

One area to look at would be to go a tad under so like 0.99ct vs 1ct that will be virtually the exact same size. However this will be firstly very difficult to get and then secondly the price will relatively be close in line. Reason for this is people cutting diamonds know that the weight will play a big role in the value of the diamond and they will cut it to get maximum value out of it understandably. So it is unlikely a cutter will cut a diamond to end up just under a threshold, this might only happen if they are trying to improve the clarity or had a chip repaired etc. in the end the prices are usually not worth going for the lower weight. These near weight stones are called light carat. If you go for between two threshold there usually lies a bunch of good options in price points. If you are not fixated on a particular weight like a 1ct (as this is mostly a mental concept of desire than of practical value ) then it might be way worthwhile to look at a 0.92ct or 0.85ct as their diameter is a bit smaller but not much and they are usually cut beautifully as the cutter don't try to fit them into a weight bracket. So be careful buying a diamond on a weight like an exact 1ct as cutters might and often would sacrifice the cut quality i.e. proportions to get the stone weight wise into a bracket to get more for it. If you go for a 1ct then make sure it is cut excellent or around 1.02-1.05ct to avoid buying diamond that is not as good as it should be. 

  I would go with mid bracket diamonds in weight if all else equal as the enticement of cutting it to fit a size bracket is not applicable and the prices around those levels are usually quite good as it is not close enough to a next bracket to push the pricing up to compensate for the initial miss on the weight. Always compare the diameters of the approximate size you want and then look around that size to see how far you can move either way to get a good balance between diameter and weight.

Remember the weight is just a measurement and a mental idea, what you want is the right diameter in the face of the diamond i.e. the size when you look down at the diamond. So this is why my next blog on cut and proportions is important, here is what counts most. So on weight look at diameter size more than carat weight as that can be misleading, remember a diamond can be cut deeper or more shallow or have a thick girdle (join between the bottom and top part of a faceted diamond) where a lot of "carat" weight can be locked in without giving you any value in looks. I recently helped a customer buy a 1ct diamond that looked like a 1.15ct size ( diameter of face was 6.8mm vs 6.5mm standard) just because of the cutting and thinner girdle with sharper angles. In the end you must see the diamond and if it's lively, diameter is good and weight between weight brackets or not bordering and practical to set in your design then great! 

As more fancy cut diamond come into fashion I though it might be of value to have the above chart showing the most major size differences. There are weight price jump brackets in between but these would be more major jumps. Also note that fancy cut diamonds are usually 10-15% cheaper if not more than round brilliant cut diamonds, so worth looking into as you can get nice sizes and they show up with big faces a lot of times. Again check the next blog on cutting as this plays a big role if not biggest in diamonds. 

David van Niekerk