The most stunning diamonds exhibit such brilliance, fire, and sparkle that it leaves everyone breathless. A diamond’s beauty is all about how well it handles the light. But what makes these stones shine the way they do? Do diamonds refract light?
As the light enters the diamond, it’s scattered and fractured, creating that famous sparkle – that’s the refraction at play. However, some diamonds might sparkle less than others. Why’s that the case?
Don’t worry. We’ve covered everything you should know about diamond’s light performance in this article. So, be sure to read it until the end!
What Is Refraction?
Refraction is generally defined as the change in the direction of a wave passing from one medium to another and is caused by its change in speed.
For instance, ocean waves travel faster in deep than in shallow water. If the wave approaches a beach diagonally, the part that’s farther from the shore will move faster than the closer part.
And as a result, the wave will swing around until it’s moving in a direction perpendicular to the beach.
We know it has nothing to do with gems and light but bear with us.
When it comes to electromagnetic waves constituting light, they are refracted when they cross the border from one transparent medium to another one due to their change in speed.
A ray of light is comprised of many wavelengths that, in combination, appear to be colorless. Upon entering a glass prism, or in our case a diamond, the different refractions of the various wavelengths fan out and apart – like in a rainbow.
The Refractive index of a diamond is 2.41, which is relatively high and gives them their sparkly characteristics. The better the diamond cut is, the more noticeable refraction of light it is. So, let’s talk about one of the most important 4Cs of diamonds – the cut.
What Is A Diamond Cut?
The cut refers to how well a gem is cut and polished. It includes how well proportioned the stone is, its symmetry, and its depth. Diamond cut isn’t referring to the actual shape of the gem – such as pear or oval shape – though.
As you might know, cut quality directly affects the diamond’s beauty and brilliance.
A well-cut gem is luminous and reflects light back to the viewer’s eyes. Conversely, a poorly cut diamond appears dull and lifeless instead of brilliant.
Differences in diamond cut significantly impact the beauty and value of the diamond – and that’s why some consider the diamond cut to be the most important of the 4Cs.
How GIA Grades Diamond Cut Quality
A professional gemologist at the GIA examines each stone under magnification to determine the cut grade:
- Excellent cut diamonds exhibit the highest level of brilliance and fire. Because nearly all of the incoming light is reflected through its table, the diamond sparkles magnificently.
- Very Good cut diamonds show exceptional brilliance and fire. A large portion of the entering light reflects through the stone’s table. To the naked eye, Very Good cut gems provide almost identical sparkle to those of Excellent grade.
- Good cut diamonds show brilliance and sparkle with a good amount of light reflecting through the table back to the viewer’s eye. These stones provide beauty at a lower price.
- Fair cut diamonds provide very little brilliance, as the light quickly leaves through the sides and bottom of the gem. Diamonds with this grade can be a good choice for smaller carats and those playing the role of side stones.
- Poor cut diamonds yield almost no sparkle, fire, or brilliance. Entering light escapes from the bottom and sides of the stone.
Learn More: Is IGI As Good As GIA?
How Cut Grade Affects A Diamond’s Price
Diamond cut prices depend on the precision and quality of the cut – mainly its proportions and symmetry.
If the facets, for example, are proportional, they will refract and reflect light back to the viewer’s eyes in fabulous fashion. Diamonds that aren’t very well cut have facets and pavilions that don’t refract and reflect light in the same spectacular way.
And trust us, the amount of light return found in an exceptionally cut diamond is worth the extra price. A diamond is less than radiant without fire and brilliance, no matter the table size or carat weight.
In other words, the diamond’s cut is the factor that most notably affects its beauty.
That’s the reason why the prices of higher-quality diamond cuts are worth every penny. Also, it’s better to spend more money on the cut than on clarity and color.
Read Also: Who Controls The Price Of Diamonds?
Factors Impacting Diamond Cut And Price
The most important element in a diamond’s value and price is its cut quality. Many factors are involved in a diamond’s cut quality, such as facets, proportions, finishing details, and the ability to reflect and refract light.
The better these elements are, the higher the quality of the stone is – thus, the higher the price. While clarity and color play an essential role in a diamond’s appearance, cut is the most critical of the 4Cs.
Here are the main factors that impact the price of a diamond:
- Proportions (table, width, and depth)
- Symmetrical facets (windows, mirrors, and steps of a diamond)
- Brilliance (brightness of light reflection)
- Fire (the dispersion of colored light)
- Scintillation (flashes of sparkle when light moves)
- Finishing details (polishing and permanent treatment)
Now let’s cover each of these factors one by one.
1. Diamond Proportions
To further understand the elements impacting a diamond’s cut quality, let’s look at proportions – mainly its table, width, and depth. These factors are measured and are excellent indicators of quality.
Proportions directly impact diamond’s ability to reflect light and showcase brilliance. They’re based on the ratios between shape, angle, and size of each diamond facet.
Various combinations of these factors affect how the diamond will interact with light, dictating its overall appearance – and its GIA grading.
About Diamond Table
The diamond table percentage is determined by dividing the table’s width by the width of the diamond. So, for example, if the table facet is 3.5 millimeters wide and the diamond diameter is 5 millimeters, the table percentage is 70%.
If the table percentage is too big, the light won’t reflect off the crown angles and facets. Vibrant reflections won’t’ be seen as the light will escape from the top of the stone – instead of reaching the viewer’s eyes.
On the flip side, if the table percentage is too low, the light will remain trapped within the diamond and be emitted through other parts of it instead of to the viewer’s eyes.
The ideal table percentage heavily depends on the diamond shape.
If you’re unsure about the actual table percentage of your diamond, visit your local jeweler. They’ll be able to walk you through the options and factors.
About Diamond Width
A diamond’s width is established by measuring from one end of the stone’s girdle to the other.
The width is most crucial when it comes to determining the length-to-width ratio, which shows how proportionate the diamond is along with its shape.
The length-to-width ratio is simply measured by dividing the length of the stone by its width.
For instance, if a diamond has 5 millimeters and a width of 3 millimeters, the length-to-width ratio is 1.67.
About Diamond Depth
Depth percentage refers to the height of the stone, from the top of the table to the culet. Depth is measured in percentage or millimeters.
Depth percentage is calculated by dividing the gem’s depth by the width.
For example, if a diamond measures 4 millimeters in depth and 4.5 millimeters in width, the depth percentage is 88.8%.
In most cases, a lower depth percentage of two gems with the same carat weight would appear more prominent because of the increased width. Conversely, a depth percentage that’s too low can make a darker appearance as it won’t reflect light as strongly.
What Happens When The Diamond Cut Is Too Deep?
When a diamond is cut too deep, light hits the pavilion at a much sharper angle resulting in immediate reflection of it to another pavilion. The light is then forced to retract and leave the stone through its bottom.
As this happens, the diamond becomes lifeless and dull.
In addition, a diamond cut that’s too deep tends to look smaller than those of an excellent cut.
What Happens When The Diamond Cut Is Too Shallow?
When a stone is cut too shallow, light hits the pavilion at a lower angle. The light passes through the gem and leaves through the sides instead of reflecting back to the viewer’s eyes through the diamond’s table.
While shallow-cut diamonds, also known as “spready diamonds,” might appear more prominent due to their table size, the light that leaves through the bottom of the gem significantly reduces its brilliance, sparkle, and fire.
2. Symmetrical Facets
The facets of a diamond are small mirrors that reflect light to our eyes. Facets surround a gem’s table – there are facets below the girdle as well as above it.
The pavilion is also made up of facets. For instance, a round brilliant diamond features 58 facets total.
The symmetry, size, and placement of the facets affect how well the stone reflects and refracts the light. A diamond with too many facets, not enough facets, or with unproportioned facets can lead to a diamond looking less brilliant.
A diamond’s brilliance is the brightness level of the white light reflection.
When you look at a gem face-up under a light source, you should see it reflect an abundance of white light. A stone that’s not symmetrical, or is cut too shallow or too deep, appears lifeless and dull instead of brilliant.
A diamond’s fire is the magnitude of colored light reflected off the facets and table.
When looking at a diamond face-up, in broad daylight, you should be able to see colored light bouncing off of the stone – and that light is called fire.
If the diamond doesn’t show colored light reflection, it has a low amount of fire.
Diamond’s scintillation refers to flashes of sparkle you see when light moves across the stone’s facets and table. The scattering of the light looks like sparkle and is a result of the light and dark areas on the surface of the diamond.
A diamond is more desirable if it has a more significant amount of scintillation. On the flip side, a stone without much scintillation can look lifeless.
6. Finishing Details
The finishing details refer to the actual craftsmanship of the diamond and consist of the gem’s permanent treatment and polishing. The polish of a diamond is the condition and quality of the facet surfaces.
A well-polished diamond creates a clear mirror for the light to reflect off of; a diamond with poor polish appears dull because the facets don’t reflect the light as strongly.
What’s The Difference Between Diamond Shape And Diamond Cut?
Many people confuse the terms “diamond cut” and “diamond shape,” but those two have distinct meanings.
- Diamond shape describes the figure or outline of the precious stone. For example, “round brilliant” and “pear-shaped” refer to the general shape and appearance of the diamond.
- Diamond cut refers to the facets, dimensions, symmetry, and reflective abilities of the stone. For example, a heart-shaped diamond might be cut deep or shallow, brilliant or dull – the actual cut differs significantly while the heart shape remains the same.
Do diamonds refract light?
Yes, they do. Refracting the light is one of the diamond’s main qualities that makes it so unique. The diamond is cut so that light enters, bounces, and bends within the precious stone – and in the end, leaves from the top of the gem back to our eyes. This concept is known as refraction.
On that note, a well-cut diamond will reflect the light perfectly within it. Diamonds are generally cut to maximize the brilliance, sparkle, fire, and overall visual beauty of the stone.
Learn More: Why Does A Diamond Sparkle?