How does Diamond Polish affect the look of a diamond?
There are 3 main categories that when combined give a diamond it’s overall cut grade. The First is the “Face-Up Appearance”. This includes the brightness, fire, and scintillation. The Second Category is “Design”. This includes weight ratio, and durability. The last category is “Craftsmanship”. This includes Diamond Polish and Diamond Symmetry.
Take a look at the pictures below, and you’ll notice white polishing marks. The diamond is not really black, it was just placed in darkfield illumination and magnified to easily demonstrate what marks or scratches diamond polishing can cause. How easily you can see these marks with your naked eye is the big question.
There are certain polishing marks that are easy to see. A mistake happens during the process, and “oops”! These of course would get a low score, but there are quite a bit more where you can’t actually see anything, and they still get average to fair marks, but not excellent or very good. Here’s why what you can’t “see” makes a huge difference to the overall brilliance and sparkle of a diamond.
In the next few sections you’ll see many types of Polishing blemishes. Such as abrasions outlining a facet, or white lines streaking across another facet, and many more. Most of these polish lines you can not see with the naked eye. You would need 10x magnification or higher. However, although you can’t see the actual mark you can certainly see it’s effect.
An Analogy to Explain Diamond Polish
A great analogy would be to look at a headlight. Look at the glass lens. The lens in this case is the diamond. The light coming through the glass lens could be compared to sunlight or room light. Now, if that headlight is perfectly clean, no wear and tear lines, no dings, no small scratches, no dirt, then the light will shine through just as it’s supposed to and give you the effect you’re looking for. Big, bold, brightness. However if the surface of the headlight is marred in anyway, the light shining through it will deflect in a way you don’t want, such as out the sides, or back down. Either way we won’t get the full light we were hoping for. We’ve all experienced dirty headlights, and how dark the road seems if they are not completely clean.
Sometimes the heat of the polishing tool gets to hot that it can create a white haze on the diamond from being burnt. Burn the glass lens of your headlight and you’ll get very dull light. When light enters a diamond, it should hit each and every facet perfectly to bounce back out the top. This is what gives you your sparkle. If the diamond is not cut correctly (such as each diamond facet not having the same symmetry) the light will bounce around in the diamond, some of the light will go back up, and some will leak out the sides and bottom, creating a very dull looking diamond. Same goes with polishing blemishes. The marks seem small, but light still deflects off everything in it’s way. We’ve all seen on T.V. where someone is in a cave or dark place, and they start using mirrors to deflect the outside sunlight down the deep cave tunnels. If the mirrors or reflecting objects are off just a bit, it could be disastrous and the light will go everywhere but where you want it to.That’s why the cut of the diamond is the single most important aspect you should consider when buying a diamond. Most grading reports will break down the cut of the diamond into smaller aspects. In fact most of the information on a diamond grading report has to do with the cut. Next being color and clarity.
Marks and blemishes diamond polishing can cause.
A tiny opening appearing as a white dot. These may or many not go beyond the surface of the diamond.
A small notch on a facet junction, usually along the girdle or culet; minute chip with no visible depth at 10X magnification.
Surface marks normally seen as a fine white line, curved or straight, on the surface of a diamond.
Area of minute scratches or pits along a facet edge producing a fuzzy white line instead of a sharp facet junction.
Parallel lines left by the polishing process; may appear white or transparent. Usually in groups. Rarely just one.
Transparent uneven texture confined to one facet; caused by polishing a facet off-grain, at the hardest direction near a cleavage plane.
Burn Mark / Burn Facet
Whitish haze across a facet or on a concentrated area caused by excessive heat during polishing or occasionally by a jeweler’s torch.
Irregular pitted or granular surface of a bruted girdle due to pits and nicks.
The Girdle is a Polish Line
Some people might be surprised to learn that the “Girdle” is considered a “Polishing Line”. It separates the top portion of the diamond (Called The Crown) from the bottom portion. (Called The Pavilion)
The Girdle is really an exaggerated example. This is because the girdle is usually large enough to almost always be visible to the naked eye. The girdle may even be polished or faceted so it will blend in better and not be so noticeable. The other polishing lines are not usually as noticeable.
How is Diamond Polish Graded?
Excellent – Very few diamond polish features / blemishes. If there is one, it’s quite difficult to see under 10x magnification face up, and you certainly won’t see anything with your unaided eye. This category may have very minute pits or nicks. Possibly small faint transparent polish lines. Again, though, you won’t see them. The overall brilliance and luster of this grade is dynamic, assuming all other cut requirements are excellent.
Very Good – Easier to see the polish features / blemishes under 10x magnification face up. However nothing that you will see with your naked eye. In this category you might find several minute pits and nicks, small abrasions, and limited transparent polish lines. The luster of this diamond, assuming the overall cut is excellent, will be brilliant.
Good – It’s quite easy to see the polish features under 10x magnification, face up. You might even notice a little with your unaided eye. At this grade, you can expect the cleanness of the diamond to be satisfactory. Unless you hold it side by side with a better grade you may not notice the difference. However the luster will be effected slightly. You can expect to see moderate to heavy transparent polish lines, white polish lines, more than a few heavy scratches, possibly even a little lizard skin texture and very very slight burns.
Although the luster will be affected, it won’t be exceedingly bad, and if you have to keep the cost of your diamond down, this may be a good place to start. However, if you go this grade, consider making sure the diamond symmetry is at least very good. Balance is the key with diamonds. You can sacrifice in some areas, but make up for them in other areas. An example would be diamond fluorescence. Fluorescence can dramatically effect your diamond for the worse if the color is in the D-F range. However if you go more tinted to save some money, say around H, I, J in color you’ll start to notice the yellow tint show through. To balance this, look for a diamond that have a moderate blue fluorescence to it. Since blue and yellow are opposites, the colors will cancel each other out, and your diamond will actually appear more white / colorless. Plus the diamond cost you less. One other trick comes to mind. If your budget doesn’t allow for a “spendy” diamond, make sure your ring has sparkling side / accent diamonds. The illusion you create from the sparkle of the side diamonds will also help offset any lack thereof in your center diamond, and there are plenty of inexpensive engagement rings out there that will do the trick.
Fair – When you hit this diamond polish grade you can expect the brilliance of the diamond WILL be effected. In fact the luster will dramatically decline. Like the headlight analogy above, there’s just too much on the surface preventing the light from going back up through the top. Not always, but mostly this grade will give you a dull diamond. Here you can expect to see heavy white polish lines, burnt facets over most of the crown and pavilion. The heavy handedness with heat tools is what you’ll usually find at the fair to poor grades.
Poor – As you may expect, this diamond has a big potential to be dull and dark. Just like the fair category, you can count on seeing plenty of burn marks made by the polishers tools. Heavy white polish lines in massive clusters. Your best bet is the crown (the top part of the diamond), and the Pavilion (bottom part of the diamond) is so heavily marred that there’s no way for light to escape except through the sides, perhaps. I would avoid this polish grade.
American Gemological Society (AGS)
Chances are, in your diamond search, you’re going to run across diamonds graded by The American Gemological Society(AGS). This is an independent gemological laboratory (second only to GIA), that uses a different scale than GIA. (Gemological Institute Of America) Their diamond grading report uses a scale from 0 to 10. (Zero to Ten) Zero is considered to be the best and is comparable to GIA’s grade of excellent. A good compromise if you are trying to maintain a good balance, and get the most bang for the buck, would be a rating of 4-5
Pictures courtesy of GIA.