The Woolfe guide to the 4C's of Diamond grading
Diamonds are carefully graded for quality in several ways. This is done by independent diamond laboratories which produce a report, also known as a certificate. The diamond grading system that laboratories use was invented by GIA, the Gemological Institute of America and this grading system has been copied by many diamond grading laboratories. GIA is accepted by the world’s top jewellers as being the strictest and most reputable gemological laboratory in the world and it is one of only two laboratories that we trust here at Woolfe. The other laboratory we trust is IGI, the International Gemological Institute.
Many people think of the four Cs when considering diamond grading, that is cut, colour, clarity and carat weight, but there are other very important factors which influence the quality and value of diamonds
The assessment of how well a diamond has been cut and polished is shown on the report in three separate grades. These are cut grade (on round brilliant cut diamonds only), polish grade and symmetry grade. Most retailers simply refer to the basic shape of a diamond when talking about cut, ie round, oval etc, but actually the skill and accuracy of the cutter has a big part to play in the beauty and value of the diamond. The cut grade in a round brilliant cut diamond indicates that it has been cut within strict parameters to reflect as much light as possible giving the brightness, fire and scintillation associated with only the most accurately cut diamonds. Polish and symmetry play their part in the cut grade and they are individually graded as well. The polish grade refers to the finish on the individual facets of the diamond and the symmetry grade refers to how symmetrically the diamond has been cut. A diamond with a lopsided cut will score badly here. There are five possible grades awarded for cut, polish and symmetry, poor, fair, good, very good and excellent. Here at Woolfe we only sell white certified diamonds with excellent or very good cut, polish and symmetry grades. We do not sell diamonds with extremely thin girdles (the widest part of the diamond), because they are vulnerable to being chipped when being worn.
This is a measurement of weight only. A whole carat is equal to a fifth of a gram. It is important to understand that it does not indicate how big the diamond looks. A well cut diamond will usually have a larger face up measurement than a poorly cut diamond and will have more brightness, fire and scintillation thus making it look bigger.
Most diamonds are not completely colourless. Absolutely white diamonds are quite rare and most diamonds have a hint of yellow or brown in them. For this reason diamonds are graded for colour between D and Z. D is the very whitest and as the grade gets lower the diamond will have a more yellow or brownish tinge. A diamond that has a colour grade of D, E or F will look colourless to a human eye. It is only as you get to G and below that the yellow or brown becomes noticeable. Virtually all the certified diamonds sold at Woolfe are in the D, E and F colourless range. There are also some rare diamonds with what is known as fancy colour. Pink and blue diamonds are highly prized and more expensive, canary yellow is another unusual fancy colour.
This refers to the internal characteristics of a diamond. Diamonds are formed in nature at very high temperatures and pressures and often have internal blemishes or inclusions which occur naturally as they form. The larger these inclusions are, the more they affect the beauty of the diamond. A diamond is rarer and more beautiful with little or no inclusions. The possible clarity grades awarded by GIA are as follows:-
Flawless – A diamond with no internal or external inclusions or blemishes whatsoever. It would take days to polish the exterior of the diamond to this ultimate standard and so only particularly large and valuable diamonds will have this much time lavished on them.
Internally Flawless – A diamond with no internal inclusions or blemishes whatsoever. The very best one can can expect.
VVS1 – Very, very slightly included, a diamond with such small inclusion that it is almost impossible to see the inclusion with 10 x magnification
VVS2 – Very, very slightly included, a diamond with such small inclusion that it is very difficult to see the inclusion with 10 x magnification
VS1 – Very slightly included, a diamond with such small inclusion that it is only possible with some difficulty to see the inclusion with 10 x magnification
VS2 – Very slightly included, a diamond with such small inclusion that it is only possible to see the inclusion with 10 x magnification
Si1- Slightly included, a diamond with small inclusion that may be seen with a naked eye
Si2 – Slightly included, a diamond with small inclusion that may be slightly easier to see with a naked eye
I1 – Obvious inclusion that detracts from the beauty of the diamond
I2 – Really obvious inclusion that detracts from the beauty of the diamond
I3 – Really obvious inclusion that very badly detracts from the beauty of the diamond
The higher the clarity grade, the more valuable and expensive the diamond. It will not be possible to see an inclusion in a round brilliant cut diamond with a clarity grade of VS2 or above. There are some diamonds with Si1 and Si2 clarity grades which have inclusions which can not be seen with a naked eye, because the inclusions are white or in a place like a facet juncture or underneath. These diamonds offer very good value and we seek them out whenever possible if the other quality factors meet our standards. Our GIA diamond graduate examines each diamond carefully before we buy it so that we do not sell diamonds with visible inclusions. We have an excellent selection of diamonds with clarity grades between internally flawless and Si.
About a third of all diamonds suffer with natural fluorescence. This tends to make a diamond look a little milky and less sparkly in any sort of UV light. Of course sunlight contains UV light and so do the new energy saving light bulbs, so most of the light the diamond will be seen in has UV light. Woolfe do not sell white certified diamonds with fluorescence.