Many diamond shapes beyond the round brilliant began as new designs that someone patented or trademarked. The princess, the radiant and the trilliant all started this way before becoming generic shapes any cutter can use. Branded cuts continue the pattern today, usually as a round or fancy shape with a changed facet arrangement and a trade name. Knowing what a patent or brand covers helps a buyer judge the stone on its own merits.
What a cut patent covers
A patent on a diamond cut protects a specific facet arrangement or method of cutting, described in drawings and claims. In the United States, a utility patent usually lasts 20 years from filing, and a design patent covers the look of an object for a shorter term. Once a patent expires, anyone can cut the design.
Patents protect the arrangement, not the beauty. A patent does not certify that a cut returns more light, and patent claims about light performance are statements by the applicant, not independent tests.
A trademark is different. It protects a name, such as a brand name for a cut, and can last as long as the owner keeps using it. Two stones can share almost the same facet plan but carry different names. Some designs carry both a patent and a trademark, and the name survives after the patent expires.
The princess cut
The princess cut is a square or slightly rectangular brilliant with pointed corners and a pavilion of chevron-shaped facets. Viewed from the side, the pavilion often looks like an inverted pyramid. Several cutters developed square brilliants in the 1960s and 1970s, and the modern princess cut took shape around 1980. It became one of the most popular fancy shapes in engagement rings.
The princess cut wastes little rough. A single octahedral crystal sawn in half yields two square-based pyramids that suit the princess shape well, so cutters keep more weight than they would cutting rounds. That helps explain why princess cuts usually cost less per carat than comparable round brilliants.
The pointed corners are its weak point. They chip easily, so most jewelers set princess cuts with V-shaped prongs or other corner protection. The gemstone settings page compares the options.
The radiant cut
Henry Grossbard patented the radiant cut in the late 1970s. It combines the outline of an emerald cut, a rectangle or square with cut corners, with brilliant-style faceting on both crown and pavilion. Most radiants have around 70 facets.
The radiant was one of the first rectangular cuts to show brilliance comparable to a round, and its trimmed corners resist chipping better than a princess. It is a common shape for fancy colored diamonds because its facet pattern intensifies face-up color. The fancy colored diamonds page explains why cutters choose shapes for color.
The Asscher cut and its revival
The Asscher cut is a square step cut with deeply cut corners, a high crown, a small table and a deep pavilion. Joseph Asscher of Amsterdam designed it in 1902. Looking down into a well-cut Asscher shows concentric squares, an effect often called a "hall of mirrors." The original design was popular in the Art Deco era, then fell out of favor.
In the early 2000s, descendants of the Asscher family introduced a modified version with more facets, marketed under its own trade name. The revival brought renewed interest in square step cuts generally. Today, "Asscher" is widely used for any square step cut with cut corners, while the family's modified design carries its own name. The Amsterdam diamond cutting page covers the Asscher firm's history, including its work on the Cullinan diamond.
The trilliant cut
The trilliant (also called trillion or trillian) is a triangular brilliant. Triangular cuts have existed for centuries, but a specific triangular brilliant design was developed and trademarked in the United States in the 1960s. Since then the name has spread as a general term.
Trilliants can have straight sides or slightly curved ones. Curved-sided trilliants are often used as center stones, and straight-sided ones as side stones next to a larger center diamond. Their sharp points need protection, like a princess.
Branded cuts today
Many retailers and manufacturers sell diamonds under trademarked cut names. Common types include:
- Modified round brilliants with extra facets or a different pavilion pattern
- Square or rectangular modified brilliants based on the princess or radiant
- Step cuts with added facets, revivals of older styles, or new outlines
- Cuts designed to show a pattern, such as a cross, star or flower, when viewed through the table
A brand can mean consistent workmanship from one maker. It can also mean a price premium for a name. The diamond still has to be judged by its proportions, symmetry, polish and the usual 4Cs.
How to evaluate a fancy cut
Labs give standard cut grades mainly for round brilliants, so fancy shapes need more judgment from the buyer. A few points help with any non-round diamond:
- Look at the stone face-up in different lighting. Watch for dark areas, especially a bow tie, a dark band across the center common in ovals, pears and marquises.
- Check the length-to-width ratio on the report. There is no single correct ratio, but very long or very stubby stones can look unbalanced.
- Look for a thick or uneven girdle, which adds hidden weight.
- Check polish and symmetry grades on the report.
- Protect corners and points in the setting.
- Compare the stone to an unbranded stone of the same shape and grades before paying extra for a name.
Step cuts, such as emerald and Asscher shapes, show clarity more readily than brilliants because their broad facets act like windows. Buyers often choose a higher clarity grade for step cuts than they would for a brilliant.
Where fancy cuts fit in cutting history
Fancy shapes became practical at scale with power saws in the early 20th century and lasers in the late 20th century, which let cutters divide rough in any direction. Optical scanning and planning software then let manufacturers model new facet arrangements before cutting. The history of diamond cutting and modern gem cutting technology pages trace these tools.
Frequently asked questions
Is the princess cut still patented?
No. The princess cut is a generic shape that any cutter can produce. Specific modified princess designs may carry their own trade names.
Do branded diamond cuts look better than standard cuts?
Some are made to tight standards and look excellent. Others differ little from generic shapes. Comparing stones side by side and reading the grading report is the reliable test.
What is the difference between a radiant and an emerald cut?
Both share a rectangular outline with cut corners. The emerald cut uses long step facets, while the radiant uses brilliant-style facets that show more sparkle and hide inclusions better.
What does a patent on a diamond cut protect?
It protects a specific facet arrangement or method for a limited term. It does not guarantee light performance or quality.