All you need to know about a diamond girdle
The girdle of a diamond can be rough, polished or faceted
The skill that goes into a rough diamond in order to produce a faceted gemstone is something to be admired. When planning the best cut for a diamond, a master diamond cutter will assess the rough stone and determine how to finish the girdle regardless of whether the diamond is a brilliant cut or a step cut. But what exactly is the diamond girdle and what impact does it have on your diamond?
A diamond girdle can be described as the outer edge of the gemstone; it’s where the crown, also known as the top part of the diamond, meets the pavilion, which is the bottom part of the anatomy of a diamond. The girdle of a diamond can be rough, polished or faceted. Here’s a more in-depth description of the three types of girdles and what effect it has on your diamond:
THE DIFFERENT TYPES OF GIRDLES:
A ROUGH GIRDLE
A rough girdle is frosty and opaque in appearance
A few decades ago most brilliant cut diamonds featured rough girdles where the girdles remained natural and unpolished. This resulted in the girdle having a ‘frosty appearance’ after it was rounded by another rough diamond. When the diamond is viewed through a jeweller’s loupe the girdle will have a frosty, white, grainy, rough and opaque appearance. The rough girdle is often referred to a ‘bearded girdle’ since it looks a lot like a man’s beard.
A POLISHED GIRDLE
Polished girdles are smooth and clean all the way around
Having a polished girdle implies that the entire outer edge of the diamond is polished into a single and clear facet. This process makes it possible for you to see right through the diamond. The entire surface area of the girdle is smooth and clean all the way around; there is no facets or any signs of roughness, only a smooth strip that makes its way all around the perimeter of the diamond.
A FACETED GIRDLE
Like the rest of the diamond, a faceted girdle is cut and polished
The most common finishing you would find on a more modern design diamond is the faceted girdle. Like the rest of the diamond, a faceted girdle is cut and polished with a series of well proportions vertical facets. But what does it mean to have a faceted girdle? During the development of the faceted girdle, small facets are cut and polished around the outside edge removing tiny feathers that were formed during the bruting process. The faceted girdle is almost unnoticeable because it reflects light causing it to blend in with the rest of the diamond.
THE RATINGS OF A GIRDLE:
Experts will view the thickness and thinness of the girdle to give the diamond a certain rating
When it comes to purchasing a diamond, the type of finish on the girdle would not necessary play a very significant role on the value of the diamond. The choice between a rough, polished or faceted girdle is one of personal preference. What is more important to note is the thinness or thickness of the girdle that has an impact on symmetry and proportions of the diamond. These ratings can in turn affect the overall cut grade of the stone. The reason? When the diamond contains a few significant variations it can make the gemstone appear disproportioned.
When a diamond is certified, experts will record the thickness and thinness of the girdle to give the diamond a certain rating. These measurements are expressed as a percentage relative to the average diameter of the diamond. The calculation is: girdle thickness (mm) divided by the average diameter of the diamond multiplied by 100 equals the girdle thickness percent.
The diamond will, therefore, fall in one of the following ranges:
Extremely thin: When a girdle is extremely thin, it might be vulnerable to chipping or even breaking. It’s important to handle the diamond with care if placed on a setting.
Very thin: This range is considered to be a ‘Very Good’ diamond proportion. Once again, it’s important to take care when placing the diamond on a setting.
Thin, Medium: When purchasing a diamond, this is what you want for your girdle. A thin to medium girdle is the ideal gemstone proportion.
Slightly thick, thick: This range is considered to be an excellent to ideal proportion of a gemstone.
Very thick: A very thick girdle means a good gemstone proportion.
Extremely thick: With an extremely thick girdle as such, your diamond might seem smaller than it actually is, since more depth is taken up by the girdle.
In the end, while the style of the girdle is influenced by personal preference, it’s important to consider the size of your girdle before purchasing a diamond. The thickness of the girdle can either be perfect or completely wrong for your diamond resulting in a stone with poor proportion and symmetry. Therefore, always have a look at the diamond certificate and what it says about the diamond girdle. Look for an overall cut grade of no less than ‘Very Good’ and try stick to a thin, medium thickness range. If in doubt, visit the Cape Town Diamond Museum for a personally guided diamond tour. Our diamond experts will gladly share their knowledge and expertise on diamonds with you.