What You Should Know About A Diamond's Cut and Angles

Think you already know everything about diamonds? While most people are aware of the extreme hardness and rarity of diamonds, what is less known are the extreme design challenges that face the diamond cutter. It takes the skill and expertise of a master diamond cutter along with the precision offered by technology to unlock the natural beauty of a diamond to its fullest potential. The cut of the diamond is considered by experts to be the most important of the four Cs.

Over the years, we often meet people who really want to know more about the cut of a diamond, its exact measurements, and how this really affects the overall beauty of the stone. There's never such thing as knowing too much when it's time to finally buy a diamond.

Let's dissect a diamond and look at each of its parts so that you have a better understanding of what you are buying:

What are the different parts of a diamond?

Polished diamonds on the market today have two main parts - the crown, which is the top portion, and the pavilion, being the bottom portion. Both are separated by the outer edge of the diamond known as the girdle.

The crown has 33 facets in total for most round diamonds. Three sets of facets consisting of:

• 8 crown main facets (aka kite or bezel facets).
• 8 star facets
• 16 upper half facets (aka upper girdle facets)
• 1 table facet

The pavilion has 24 facets in total (25 if there’s a culet). Two sets of facets consisting of:

• 8 pavilion main facets
• 16 lower half facets
• 1 culet facet (Most brilliant cut diamonds do not in fact have culet facets today).

The illustration is of the round brilliant cut diamond. The traditional round brilliant diamond has in total 57 facets (33+24) or 58. The 58th is a tiny flat facet at the bottom of the pavilion that’s known as the culet.

Within the top portion of the diamond - the crown - there are crown angles which measure the angle in which the facets intersect the girdle plane. The crown angle provides an important escape route for the reflected internal light to be viewed. In the illustration below, you can see the arrows indicating what happens when light enters the diamond reflecting and refracting as it leaves the diamond.

Why is a well-proportioned diamond so crucial?

The pavillion of the diamond is the cone shaped section of the diamond under the girdle. The distance from the bottom of the girdle to the culet is the pavilion depth.

When the pavilion facets of a diamond are angled too steep, they will not reflect maximum light back to the viewer. In a well-proportioned diamond, a high percentage of the light rays reflect back into the eye as brightness. If the diamond is too shallow or too deep, a high percentage of the light rays are lost out the sides or the bottom of the stone.

A well-cut diamond will direct more light back up through the crown. The ratios and proportions of various diamond dimensions in relation to each other are what impact the brilliance and scintillation of the stone most significantly.

How does a diamond's cut contribute to its beauty?

Though extremely difficult to quantify, the cut of any diamond has three attributes: brilliance (the total light reflected from a diamond), fire (the dispersion of light into the colors of the spectrum), and scintillation (the flashes of light, or sparkle). The brilliance, fire and scintillation contribute to a complex interaction of what make the diamond attractive. The type of lighting (a well lit room or out doors with natural light all around) is equally important to the viewer’s perception. The true beauty of the diamond is made possible by the cut.

Many gemological sources express this basic conclusion regarding the crown and pavillion angle of the diamond. A shallow crown angle can have more white light return and a crown angle tending toward the steep side many times will show more fire. The facets above the girdle (outer edge of the diamond) act as windows and the facets below the girdle (the pavillion) act as mirrors reflecting the light back to the viewer. It is the combination between the two that produce a balance between brilliance and fire while at the same time avoiding light to be lost. If the light that enters into the diamond does not return, the sparkle is lessened.

And how does this affect your diamond-buying experience?

Now that you know all of this, you can see why it's incredibly important to see a diamond in person rather than rely on what is said on a piece of paper. Buying from online retailers like Blue Nile can put you at risk of buying a diamond that is not cut properly, even if you are comparing what seems to be two comparable diamonds. Unfortunately, the "cut grades" shown on laboratory reports like GIA are extremely broad, which means two diamonds with the same cut grade can look dramatically different to the eye. Seeing a diamond in person is the best way to closely inspect it and make sure you are getting the best possible stone for your money.

Interested in seeing diamonds up-close and in person? Come pay us a visit, and we'll show you diamonds under magnification so you can see exactly what they look like. No pressure and no obligation!