How to Buy a Diamond
A Guide to Diamond Cuts & Shapes
The "cut" of a diamond is perhaps a buyer's most important consideration. This is because the quality of the cut will directly determine the stone's overall brilliance and beauty. Referring to more than just the diamond's shape, a cut deals with the stone much more holistically. A diamond's shape is the overall outline or external wrapper; a diamond's cut is its entire anatomy.
What Is a Diamond's Cut?
A diamond's cut refers to its facets and angles, number, proportions, and symmetry, affecting how light reflects out of the stone. The grade for a diamond's cut ranges from excellent (reflecting as much light as possible) to poor (much light lost out of the sides or bottom of the diamond). A skillfully cut diamond will reflect as much light as possible out of the table (top face) of the crystal and thus appear fiery and brilliant. This effect on brilliance directly affects the value of a diamond and is an essential factor to consider when evaluating one for purchase. This illustration shows how diamonds with the same shape can have very different cuts, which affect the light reflected out of the table.
The Gemological Institute of America has a tool that shows the effect the cut has on brilliance. Move the sliding bar to see a sketch of a diamond with different cut grades.
How Is a Diamond's Cut Appraised?
The quality of a diamond's cut is held to an "ideal" standard, first developed by famed Belgian diamond cutter Marcel Tolkowsky in 1919. An "ideal cut diamond," as named by Tolkowsky, is a diamond of unmatched brilliance that is able to perfectly reflect any light that enters it. Tolkowsky determined the necessary proportions, angles, symmetry, polish, and fluorescence essential for a diamond to achieve this ideal grade through his calculations. Tolkowsky produced such a gem; the modern brilliant cut diamond, his magnum opus.
While other ideal calculations have been developed and accepted over the decades, Tolkowsky's basic formula remains the industry guideline through which all diamond cuts are appraised. The brilliant-cut also remains the most popular diamond cut over a century later, accounting for over 70% of diamonds sold worldwide.
What Is Diamond's Shape?
The diamond shape is the geometric outline that impacts the overall appearance and physical form of the stone. Besides the four Cs (cut, clarity, carat weight, and color, the shape is important to consider when when shopping for these precious gemstones. Here's everything you need to know about diamond cuts and shapes to help you find the stunning rock you've always desired.
Diamond Cut vs. Shape
It's important to remember that diamond cut and diamond shape are two unique attributes of the stone. The cut determines how the stone facets reflect light, while the shape influences its overall look.
Diamond shapes fall into two major categories: round and fancy shapes. The round diamond is a timeless shape that highlights the dazzling brilliance of the stone. All shapes, excluding round, fall in the fancy category and include princess, pear-shaped, cushion, oval, asscher, and marquise.
What Is the Most Popular Diamond Cut?
The round brilliant is the most popular diamond shape and cut, with many sources citing three-fourths of all diamonds sold are of this type. This could be for several reasons. Most rough diamonds are shaped such that two brilliant round diamonds can be cut with the least amount of crystal lost. Also, the round brilliant and the princess (which is the next most popular) are common because they reflect light best and are thus the most brilliant for their size. Crystals that are not symmetrically formed or have awkwardly located inclusions are often cut into what is called a "fancy cut" or a cut other than a round brilliant.
A Little About Branded Shapes
There are dozens more diamond shapes than the ten most common, yet some are mostly unknown outside the industry. Many of these are patented and kept exclusive by their owners. For example, a Jupiter cut has five sides, a Hexagon or Half Dutch Rose cut has six, the Queen and the Baroness cut have eight sides, and the bead cut looks (seriously) like a disco ball. The Tulip, Bullet, Boat Shaped Rose, Genesistar, and Fan are unusual shapes rarely seen.
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