Diamonds exist in structural elements that are set in such a way that every component influences the fire, brilliance, and scintillation of the stone. As such, an imperfection in any of these aspects significantly affects the overall light and color performance, as well as the visual appeal of the diamond.
If you’re planning to buy a diamond, the chances are that you’re already acquainted with the Four Cs – color, carat weight, cut, and clarity. Indeed, profound knowledge of the four Cs is invaluable during any diamond shopping experience. However, it isn’t enough in helping you to hone in on the right stone for you.
When it comes to a diamond structure, numerous other aspects make a world of difference in terms of helping you to choose a stone that’s near-perfect in every way. One such element is the crown. And in this post, we shall focus our attention on the crown angle, how to calculate it, and what the ideal diamond crown angle should be. But first things first.
Relevant Glossary Terms
Diameter – The width of a diamond as measured through its girdle
Table – The largest facet of a diamond, which usually occurs at the top of the stone
Culet – The facet at the bottom tip of a diamond. The ideal culet is never visible to the naked eye and is often graded either Small or None
Depth – The height of a diamond from its culet to the table
Girdle – The narrow band that exists around the widest part of a diamond.
Pavilion – The bottom part of a diamond, from the girdle to the culet.
Crown – The top part of a diamond, from the girdle to the table.
More About a Diamond’s Crown and Crown Angle
As we’ve already mentioned, a diamond crown is the portion that spans from the table to the girdle of the stone. It’s aptly called the crown because if you view the structure from the top, the diamond crown looks like an actual crown that’s placed upside down.
The crown of a diamond plays a crucial role in influencing the light performance of the diamond. That’s because it’s the part that handles the largest amount of light entering or leaving the stone. You can look at the crown, along with the table, as the window of a diamond.
The crown has two fundamental aspects that determine the fire and brilliance of a diamond – Crown Height and Crown Angle.
A diamond’s crown height refers to the linear distance between the table and the girdle. After determining the crown height, you express it in relation to the girdle diameter of the diamond. Usually, the average crown height is expressed to the nearest 0.5%.
On the other hand, the crown angle of a diamond refers to the angle that’s bound by the bezel facet of the diamond and the girdle. The crown angle is the most significant factor that influences how light enters the crown, and subsequently, how the entire structure of the diamond handles that light.
A shallow crown angle makes the crown appear flatter. That causes reduced light penetration and increased light leakage. And the net effect is diminished sparkle and brightness of the stone.
Similarly, an overly deep crown angle makes the crown appear dull, adversely affecting the light-handling performance of the stone. That underscores the importance of selecting a diamond with an ideal crown angle.
Now, besides allowing light into and out of a diamond, the crown angle also determines how light travels to the pavilion. As light strikes the diamond at the angle, it’s refracted, so that the light can travel down to the pavilion.
Lastly, through the crown angle, light is dispersed into different colors and hues, which impacts the scintillation of a diamond.
How to Calculate a Diamond’s Crown Angle
To calculate the crown angle of a diamond, you’ll first need to determine the Crown Depth, Diamond’s Table, as well as the Pavilion Angle. All of these units should be expressed as percentages of the average diameter of the diamond.
Calculating the Pavilion Angle of a Diamond
- Determine the pavilion depth of the diamond and enter your answer in a scientific calculator
- Divide the answer by 50
- Check for the Tan – 1 button on your calculator. Usually, this symbol appears in small letters above the Tan button. In some calculators, you may need to press and hold the Shift button as you press the Tan key. The answer that you get is the actual pavilion angle expressed in degrees.
Calculating the Crown Angle of a Diamond
- Divide the Table of the diamond by 100
- Subtract your answer from 1
- Multiply the answer by 50
- Divide the Crown Depth by your answer above
- On your calculator press the Tan – 1 button. The answer that you get is the actual crown angle, expressed in degrees.
The above formula only applies to round brilliant cut diamonds that don’t contain culets. If the diamond has a culet, you’ll need to use the crown angle formula to calculate the pavilion angle. As you do, you’ll now factor in culet as opposed to the table.
What’s The Ideal Diamond Crown Angle? When determining the ideal crown angle, the general formula is that the higher the diamond crown, the greater its crown angle. As you shall find, most diamonds have crown angles that range from 25° to 35°.
If the crown angle is shallower than 25°, the diamond may look brighter. However, such stones are more prone to chipping compared to those with higher crown angles. To prevent damage, you may need to set diamonds with shallower crown angles in mountings that protect the girdle area. A perfect setting for such diamonds is the bezel settings. Alternatively, you may consider other mounting options where the diamond is less susceptible to damage. Examples include pendants and earrings.
On the other hand, diamonds with higher crown angles are considered stronger and less prone to chipping. Such stones are excellent both in jewelry and as loose diamonds. But one notable drawback to steeper crown angles is that they make the diamond look lumpy, adversely impacting its fire and brilliance.
To arrive at the ideal crown angle, you would first need to work out the diamond’s pavilion angle. Ideal pavilion angles usually range from 40.6 to 41 degrees. That’s the range within which a diamond handles light optimally. Shallower crown angles should correspond with steeper pavilion angles and vice versa.
In terms of the crown angle, always insist on an angle closer to 34° if you’re looking for more brilliance, and an angle closer to 35° for more fire. Based on the relationship between crown angles and pavilion angles, the crown angle of 34° will be ideal if you match it with a steeper pavilion angle, i.e. 41°.
Evidently, calculating the crown angle of a diamond isn’t a walk in the park. Nonetheless, you must understand how to go about it before buying a diamond. And that’s for the simple reason that the fire and brilliance of the stone depends on its crown angle.