Diamonds are the superheroes of the gemstone world. They’re basically indestructible and have been known to save the day (ask any guy who’s been in the doghouse).
Like most superheroes, diamonds have extraordinary powers. We’re not talking about the 4Cs here necessarily (although cut comes into play). These are three other lesser-known attributes that contribute to a diamond’s beauty: brilliance, fire and scintillation.
You’ll want to get to know these three really well. They’re the BOOM! ZAP! WOW! effect that will have the woman of your dreams gobsmacked over the ring and utterly smitten with you.
Diamond Superpower No. 1: Brilliance
Brilliance—also called brightness—is the first thing you notice about a diamond. Some even say a diamond can’t be considered beautiful without it. It’s the awesome effect of all the internal and external white light reflected from a diamond’s facets back to your eyes.
Diamond Superpower No. 2: Fire
Fire is one of the most magical effects of a diamond. It’s a burst of colors much like “fireworks.” This rainbow effect is a result of light dispersion. When white light passes through a transparent medium such as diamond, the stone acts like a prism, splitting the light into the seven colors of the spectrum. The diamond’s facets then scatter that brilliant color in every direction.
Diamond Superpower No. 3: Scintillation
Scintillation is a sexy word for sparkle, or flashes of light. As a diamond moves in the light, its facets reflect the light on each other. This produces a pattern of bright and dark areas in the diamond that cause these flashes of light. When there’s an even pattern of bright and dark areas causing the flashes of light to be balanced in size, scintillation is at its best. Scintillation also includes brilliance and fire, resulting in a mosaic of light in motion.
How Diamond Cut Is Assessed
These “superpowers” are three of seven components that the Gemological Institute of America (GIA) individually assesses to determine the quality of a diamond’s cut. Cut is one of the 4Cs that form the basis of the GIA’s International Diamond Grading System, considered the universal standard for diamonds.
According to Al Gilbertson, project manager of diamond-cut research at the GIA (who was also part of the team that developed the GIA Cut Grading System), brilliance, fire and scintillation are essential in creating a diamond’s “face-up appearance.” Face-up appearance refers to how a diamond would look from above, as if set in an engagement ring.
In addition to brilliance, fire and scintillation, a diamond’s proportions also contribute to its face-up appearance. These include such things as the angles of a diamond’s crown (top portion) and pavilion (bottom portion), as well as the measurements of its facets. They each influence how light behaves as it passes through a diamond and back to your eyes.
A GIA Diamond Grading Report shows you the cut grade a diamond received. The higher the grade, the better the diamond’s brilliance, fire and scintillation. © Gemological Institute of America
Weight ratio and durability are two other components that affect diamond cut. Weight ratio represents a diamond’s weight in relation to the diameter of its girdle (the intersection of the diamond's crown and pavilion that defines its perimeter). The girdle’s diameter is basically the width of the diamond if you’re looking down on it, also known as its “face-up size.” The rule of thumb is that a diamond should not weigh more than its face-up size would indicate.
For instance, say you have two diamonds with the same average girdle diameter, so they appear to have the same face-up size. However, one diamond has greater depth or a thicker girdle, so it weighs more. The added weight will not make the diamond have better brilliance, fire and scintillation, but it will jack up the cost. On the other hand, you don’t want to sacrifice weight with a girdle that’s too thin, for example, because that can affect the diamond’s durability, making it more vulnerable to damage.
Symmetry, meanwhile, is defined as the exactness of a finished diamond’s shape and the arrangement and placement of its facets. A symmetrical diamond has an even display of brightness, fire and scintillation. In contrast, a diamond with poor symmetry might misdirect the light that enters it. This will send the light off at odd angles and reduce the diamond’s light performance.
Polish refers to the overall quality and condition of a diamond’s facet surfaces. If there’s any roughness or exterior blemishes on the facets, these can act like speed bumps, interrupting the light and bouncing it in all the wrong directions.
GIA Cut Grades Explained
Once the seven components of brilliance, fire, scintillation, weight ratio, durability, symmetry and polish are assessed, the GIA gives the diamond a cut grade based on a scale of Excellent, Very Good, Good, Fair and Poor.
From left: Excellent, Good and Poor diamond cut grades according to the Gemological Institute of America.
A diamond with an Excellent cut grade (left) is one of the most brilliant. The reflections appear bright, crisp and well balanced due to the even pattern and outstanding contrast between light and dark areas. This is an extremely attractive diamond and can carry a higher price tag.
A diamond with a Good cut grade (center) can also be beautiful, but is more so-so. The reflections aren’t as bright, crisp or balanced as the diamond with an Excellent cut. There’s also more darkening around the center.
The diamond with the Poor cut grade (right) is meh. There are more dark areas than light, and the reflections are neither sharp nor balanced. The light-performance is inferior and the diamond is basically dull.
Judging Diamonds Beyond Cut Grades
You can find the GIA’s cut grades on its independent Diamond Grading Report (top). This report also maps a diamond’s proportions, details its measurements and indicates its additional “Cs”—color, clarity and carat weight—among other things.
Other organizations, such as the American Gem Society (AGS), which founded the nonprofit AGS Laboratories, also offer independent diamond-grading reports. Its Platinum Light Performance Diamond Quality Document (above), for example, offers similar information to the GIA report, albeit with its own grading system. It also provides a visual representation of how a diamond handles light.
According to AGS Executive Director Jason Quick, you should always select diamonds that come with a grading report from a reputable diamond-grading lab. You should also shop for diamonds with a reputable jeweler or gemstone dealer. Look for one who’s credentialed and receives ongoing education on the jewelry industry. You can start your search at the GIA, the AGS or at Jewelers of America.
A jeweler or gemstone dealer can help you look beyond the information in the grading report to understand all the different characteristics of a diamond. He or she can also help you decide how to trade off between features so you can get what’s important to you in a diamond while matching your budget.
It’s also important to see diamonds in person so you can compare them next to each other under different lighting. According to the GIA’s Gilbertson, brilliance should be judged in diffused light (not spot lighting), fire in spot lighting (it can rarely be seen in diffused light) and scintillation in both lighting types.
Just as important, carefully observe all the qualities of the diamonds you’re considering. No two diamonds are alike, even within the same cut grade. You might like the brilliance and fire of one, the scintillation of another and perhaps the color and shape of another. Beauty is ultimately in the eye of the beholder. Find the one that best speaks to her.
Brilliance, fire and scintillation are the “life” of a diamond. How lively they are depends on the quality of a diamond’s cut. Look for diamonds with higher cut grades and compare them under proper lighting until you find the one she loves. Then pat yourself on the back. You’ve earned your cape.