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How to Buy a Quality Diamond

How to Buy a Quality Diamond

What Affects Diamond Quality?

A diamond’s beauty comes from both nature and nurture. Nature creates diamonds of different colors and with different inclusions. Humans cut the rough, choosing which of the 4Cs (Cut, Color, Clarity and Carat Weight) to prioritize. Should the cutter cut most of the inclusions away to get a high-clarity stone? Or should the cutter try to keep the diamond as large as possible? The quality of a diamond therefore depends on both the raw material and what cutters and polishers choose to do with the diamond. Of the 4Cs, only cut, color and clarity determine diamond quality. Carat doesn’t, because a tiny diamond can be as beautiful and well-crafted as a much larger diamond. Of the 4Cs, only cut is completely within human control for natural, untreated diamonds, because cut is determined by the quality of craftsmanship.

What is Diamond Shape Quality?

It’s easy to evaluate the shape quality of round brilliant diamonds. Round brilliant diamonds should be—well, round! Most round brilliant diamonds, especially those with Excellent or Very Good Cut grades, are very round, or at least so round that you can’t detect any variance with the unaided eye.

Fancy cut diamonds are where things get more complex. They don’t receive cut grades from GIA, because there is such a wide variety of shapes and cutting styles, each with its own length-to-width ratios and set of standards. Personal preference plays a big part, too. Here are 4 things to look out for in fancy shapes:

How to choose a Quality Diamond

Length-to-Width Ratio: The L-to-W ratio is the relationship between the length and width of a fancy shape, with the width expressed as the number one. Most people find certain ratios more attractive than others. For example, emerald cuts, rectangular cushion cuts and pears are most popular in L-to-W ratios between 1.50:1 and 1.75:1. L-to-W ratios are also important to consider because gems that are too long and narrow are prone to breaking.

Line Symmetry: For hearts and pears, the diamond’s outline should be the same on both sides when you draw a line down the middle. For ovals, squares, rectangular cuts and marquises, the diamond’s outline should be the same on each side vertically and horizontally. Symmetry makes a diamond look crisp and neat and contributes to maximizing a diamond’s brilliance. A fancy cut diamond’s GIA grading report does not contain a cut grade but does tell you the stone’s symmetry and polish grades.

Smooth Curves: Curved shapes like hearts, pears and ovals should have full, rounded “lobes” or “shoulders.” Curves should flow smoothly and not have harsh-looking flat spots.

Defined Shape: It should be obvious what shape a diamond is. A heart, for example, should have a defined cleft and crisp opposing point and not look like a flat pear. The attractiveness of a diamond’s shape can sometimes depend on ratio. An oval with too low of a length-to-width ratio might look like an uneven round.

What is Diamond Cut Quality?

Cut quality refers to how well a diamond’s proportions, design and finish work together to create a beautiful diamond. Proportion has to do with the angles and relative size of a diamond’s facets. Design refers to a diamond’s weight ratio (a diamond can have too much or too little weight for its diameter) and durability (the risk of damage due to vulnerable thin areas). Finish consists of two factors—polish (the quality and neatness of facet surfaces) and symmetry (the arrangement and placement of facets). Combined, these factors reflect the quality of workmanship that went into cutting a diamond. Cut quality is important because it affects how a diamond interacts with light, therefore determining a diamond’s brightness, fire and scintillation.

What are brightness, fire and scintillation and why do they matter?

Briefly, brightness is the white light that a diamond reflects from its facets back to the viewer’s eyes. Fire is the colorful flashes that a viewer sees when a diamond breaks up white light into spectral colors. Scintillation is the sparkle and pattern of light and dark areas that viewers see when the diamond or the viewer moves.

These are the three factors that help a diamond display a spectacular light show.

Round brilliant diamonds can receive cut grades from GIA, while fancy cut diamonds don’t. Whether your diamond has a cut grade or not, here’s how to check your diamond for cut quality factors:

How to Buy a Quality Diamond

Check your diamond’s brightness and scintillation under diffused (white) light. Does your diamond reflect back a lot of white light (brightness)? Does it flash a lot when you turn it from side to side (scintillation)? Are the bright and dark areas evenly distributed (pattern)? If the answer is yes, that means your diamond was well-cut.

Check your diamond’s fire under incandescent lighting. Does your diamond flash with lots of fire? You want a diamond with as much fire as possible in all the colors of the rainbow.

Look at your diamond under different lighting. Lighting environments change its appearance dramatically from diffused to spot lighting. Does it look good in a restaurant, outdoors, in your office? If your diamond looks amazing under different light sources, chances are you’ve got a quality diamond!

What is Diamond Color Quality?

Except for very rare fancy white color diamonds, what most people call “white” diamonds are actually colorless diamonds. And most colorless diamonds aren’t actually colorless but have hints of yellow, gray or brown. That’s why GIA created a D-to-Z color grading scale — to tell people how much (or how little) color a diamond contains.

What is Diamond Clarity Quality?

Most diamonds have inclusions that can be seen under 10X magnification—trapped crystals, structural irregularities, etc.—that result from their formation process. These inclusions or clarity characteristics can help identify a diamond as natural and tell scientists a lot about Earth. But most consumers want their diamonds as clear as possible. That’s why GIA came up with the diamond clarity grading scale, which ranges from Flawless and Internally Flawless all the way down to Included. But even Flawless diamonds may not be completely flawless. Flawless just means that no inclusions and blemishes are visible at 10x magnification.

Most diamonds, down to VS2 or even SI1, don’t have inclusions that are easily visible to the unaided eye. The inclusions inside an SI2 or an I (Included) clarity diamond, on the other hand, will be more easily seen by the unaided eye. Of course, this also depends on the vision of the person in question! But in general, budget-conscious consumers can save money by buying a comparable diamond in the VS or SI range; it will likely appear similar with the unaided eye to a diamond with a higher clarity grade. However, if you or the diamond recipient is a perfectionist, you might want to consider clarity grades of VVS2 and above, but know that you will also have to pay a premium.

The grades in GIA grading reports show you how your diamond fares on a range of grades for color and clarity (and cut for round brilliants). At the end of the day, however, the diamond you should choose should be whichever diamond you think looks best (after comparing with a lot of other diamonds, of course).


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