It’s a well known fact that a diamond’s sparkle is simply undeniable! While it may come as a shock to some—rough, also known as natural diamonds, look nothing like the perfectly polished centerpieces of engagement rings found in jewelry stores around the country. In fact, natural diamonds are actually rather dull! So what is the cause of this gemstone’s scintillating shimmer? The diamond’s sensational sparkle stems from its unique ability to refract and reflect light, which is dependent on each diamond’s proportions, symmetry, polish and ultimate cut grade—all of which are determined during the cutting and polishing processes.
While a diamond’s cut determines the stone’s overall shape, the quality of the diamond’s cut is what ultimately determines how effectively the diamond will be able to reflect light. Diamond cut quality, also known as Cut Grade, is a measure used quite often by the jewelry industry to determine a diamond’s light performance (its ability to absorb and reflect light), by rating each diamond on a scale ranging from Poor to Ideal. If a diamond’s cut is too shallow, light will leak out of the culet (a diamond’s bottom tip), whereas if a diamond’s cut is too deep, light will escape out of the gem’s sides. Cut Grades rank as follows:
- Poor Cut: diamonds of this grade are generally cut too deep, wide, shallow or narrow, causing them to lose the majority of the light that has entered the diamond through the culet (the gem’s bottom tip), or one of the gem’s sides.
- Fair Cut: represents approximately the top 35% of all diamonds (based on quality of cut). Fair cut diamonds possess sub-par brilliance to that of a good cut diamond, however fair cut diamonds are still relatively high quality gemstones.
- Good Cut: diamonds of this caliber reflect most of the light that enters. However as it reflects less light than a very good cut or ideal cut diamond, good cut diamonds are sold at a lower price than very good or ideal cut diamonds. Good cut diamonds represent approximately the top 25% of all diamonds (based on quality of cut).
- Very Good Cut: reflects the majority of light, therefore this cut is sold at a higher price point than good cut diamonds. Very good cut diamonds represent approximately the top 15% of all diamonds (based on quality of cut).
- Ideal Cut: a rare, truly exquisite cut, wherein the diamond reflects nearly all of the light that enters. Ideal cut diamonds represent approximately the top 3% of all diamonds (based on quality of cut). Every facet of an ideal cut diamond is cut to perfectly precise proportions, ensuring perfect symmetry and an “ideal” balance between the stone’s brilliance and dispersion of light.
Polish, the final determining factor of a diamond’s stunning sparkle, is graded in a similar fashion to Cut Grade. Polish Grades range from poor to ideal—where the facets on a diamond graded as “poor” may reduce the intensity of light reflected from the diamond in question, along with the intensity of the light refracted into and out of the aforementioned diamond. A diamond’s Cut Grade and Polish Grade can both be found in its GIA report.
It’s a well known fact that the speed of light is constant, however, the speed of light is actually slowed upon entering a diamond, due to the way light interacts with the electrons present in a diamond and because of this gemstone’s dense anatomical composition. Therefore, although light travels faster than 186,000 miles per second, due to this unusual phenomenon, light entering a diamond is slowed to nearly half that speed.
As light strikes a polished diamond’s surface, it will either enter or reflect off of the diamond’s Table (the large, flat surface on the top of a diamond). The light’s ratio of reflection verses retention varies with each polished diamond, based largely on its Cut Grade. Upon entry, light is directed down into the Pavilion by the diamond’s Crown (the upper portion of the gemstone). The Crown acts as a metaphorical window, responsible for gathering as much light as possible and directing the light down to the diamond’s Pavilion. The lower portion of a diamond, also known as its Pavilion, captures the aforementioned light and focuses it before directing the light back up to the diamond’s Table, where light leaves the diamond once more.
Now that we’ve discovered the factors responsible for determining a diamond’s shimmering beauty and followed the path light takes to create that sought-after glimmer, one question remains—what does sparkle even mean? This iconic sparkle is ultimately a combination of a diamond’s dazzling dispersion, fire, scintillation and brilliance.
A diamond’s dispersion refers to the separation of white light into a wide spectrum of colors—each taking a separate path due to the intense level of refraction taking place. A diamond’s fire refers to the flashes of color reflected out of a diamond as a result of dispersion. Scintillation refers to the intense sparkle created when a diamond is moved from side to side. As light initially enters the diamond, a portion the light reflects off of the interior walls into the center of the stone. The light that bounces off the diamond’s inner walls is called Scintillation. Last but not least, a diamond’s Brilliance refers to its overall ability to reflect the maximum amount of light possible throughout this entire process. High-quality diamonds have a higher rate of light return, which leads to a stunning fire effect, intense scintillation, truly dazzling brilliance—and ultimately a spectacular sparkle!